When you say vented to the roof, do you mean into the attic UNDER the roof, or through the roof with a duct up through a roof jack into a roof hood ? Hopefully the latter, otherwise you have the likely source of the problem. You are clearly getting moisture in this area still, so more insulation will not help and may hurt - insulation does not stop moisture but does trap it, particularly if you add enough tht the freezing front moves well down into the insulation, so vapor coming up from the house freezes in the insulation (making it wet when it thaws) rather than venting into the attic and evaporating from there. You need an expert check on the bathroom area - that the fan unit and any light fixtures are tighly sealed to the vapor barrier. Usually they are installed with about a 1/4-1/2 inch void all around for ease of installation, and not sealed at all, so moist bathroom air vents around themm into the attic. Then the fan unit needs checking for openings - many have openings in the plastic or metal case from manufacturing that are not sealed but should be.

Do NOT use any type of unit that, because of big lights or heat lamp, says it has to be vented and cannot be sealed in, because moist air goes right up through it. Then the duct from the fan up through the roof needs checking for leaks (and should be insulated, at least if your attic goes below freezing ever), and should have a roof jack where it penetrates the attic - a rubber seal in a metal plate that fits tightly around the duct, so the air blown into the vent hood on the roof cannot circulate back down into the attic. how to clean your laptop without compressed airMost installers just cut about a 1 foot opening in the roof (especially if they can install the duct that way without having to crawl around in itchy attic insulation), run the duct up through it into the roof hood, and walk away. portable air purifier mask

That leaves that big opening in the roof sheathing for the wet air and condensation in the hood to corculate right back down into the attic. Some installers (like my house whenn I first bought it) really take the easy route and don't even connect the duct to the hood - they just terminate it a foot or so below the sheathing so ALL the moist air goes into the attic.vision air purifier I would also check the kitchen and any other bathroom fans for the same leak sources or improper installation, and make sure all vent pipes are intact to above the roof, and that there are no furnace or HVAC ducts disconnected or damaged that could be adding moisture. Also look around all roof penetrations for ducts and pipes for staining on the underside of the sheathing, which would be indicative of roof hood or jack leaks that should be repaired. (Hopefully, with a new roof you would not have any). The area most affected should have the insulation moved away and checked to see if the vapor barrier has holes or tears, openings around pipes, ducts, light boxes or wiring, or was maybe totally torn out by some prior workman.

If your vapor barrier is not effective, moist household air will move into the attic almost year around, but especially in cold weather, carrying moisture into the attic, where it will condense and cause mold. Also - if you have a fireplace chase (wood boxout around metal chimney) in that area, it may connect to the house in the firebox area and be open to the attic (which is a real fire spread hazard but for some reason is not contrary to code), letting household air flow by that route. The mold should be brushed and vacuumed away, then treated - there are commercial sprays that are fungicides that commercial mold and mildew removal contractors have, a sprayed chlorine bleach and borax solution has also been shown to work but you would have to have an air supplied respirator and chemical suit to work with that, which only professional remediation contractors have. Do NOT paint the area - especially the underside of the roof sheathing and trusses. They needs to be able to breathe, not have any moisture from above locked in.

Stains in the attic (assuming this is an unoccupied area) can be bleached, and then if you want the evidence to go away and make it easier to tell if there is new staining or mold, sanded to remove the worst of them. Stains on areas visible from the outside like walls and rafters can be treated with Chlorine bleach (beware of dripping on good finishes below), painted with Kilz or similar anti-fungal primer, then painted. Stains on the underside of the sheathing visible in the soffit area can be bleached and then when dry, sanded away. Ventilation is essential, but without removing the source of most the moisture you will not win this war no matter how many times you battle it. While I would guess the fans and vents are the problem, is there anything different about the attic ventilation to this area versus the other parts of the roof - soffit covers, blocked eave openings, insulation-clogged bug screening or soffit cover openings, lack of air chutes or eave baffles, insulation pushed up against eave opening or up against roof, horizontal blocking that prevents or obstructs airflow

, no ridge vent above it, etc ? If you are not able to find an obvious source of the moisture, I woud consider getting a thermal IR scan of the attic. For typically about $200-300 an energy conservation expert with thermal scanner can scan the attic (might have to be done at night or VERY early morning if done in summertime, to accentuate the temp difference between house air and attic air, unless you have AC in which case turning the AC down low and blower on full can work by pushing cold air rather than hot up through any gaps or voids. If you have that done, check on price to add in the rest of the house too - probably not more than about $100 more, and can show you where your air leaks and poor insulation air. You should try to get one who can provide the entire scan to you on CD or DVD, so you can review it in the future. Here is a link to some images so you know what I am talking about -The presence of mold in an HVAC system is a common complaint.  Mold is a sneaky little bugger.  

It can grow and proliferate and make building occupants sick without ever being seen.   And the fastest way to spread mold through a building is through a forced-air HVAC system.The reason this complaint is so common is that mold is always present in your buildings and your HVAC system to the extent that it is present in your building’s environment.   There will be more mold in humid weather and less in dry weather.   You will never get rid of it completely, but you can control it.   All it needs to grow is moisture and food.   Take those away and the mold goes away. for residential and light commercial mold remediation productsAccording to the U.S. EPA, you should routinely inspect your HVAC systems, not just for mold, but for moisture.   Look at drain and condensate pans to make sure they are draining properly.   If they are plugged, the moisture that accumulates will become a mold factory.  Also make sure that all HVAC ducts and system components such as air handlers, blowers, plenums and the like are free of any moisture.

If, despite regularly inspecting your system, you are still getting complaints about it (mold starts to grow in as little as 48 hours), here are some tips for cleaning it up:1.) Turn off your HVAC system.2.) Everyone involved in this cleaning should wear at least an N-95 respirator3.) Replace anything porous, such as filters or insulation that has become wet.  Double-bag the waste using at 6-mil or thicker plastic bags.4.) Use wet vacuums to clean out any standing water.5.) Use an EPA registered disinfectant labelled for HVAC use to clean non porous surfaces (Duct work, coils, plenums, pans, etc) of mold, mildew and other dirt. BBJ MMR-II ready-to-use disinfectant and mold cleaner will kill and remove mold, mildew and odor causing bacteria.6.) As an added measure, isolate each section of ductwork you clean with bladders so the spores you stir up during cleaning don’t spread to other parts of the system or the building. Fog the area with an EPA registered disinfectant.7.) Apply a mold and mildew inhibitor to all components of the HVAC systems.