True, but it helps to have a trailer with vents(not on the roof!)
Yes, vents should help some. The problem with sweating seems to be when snow and/or ice is piled on the roof and the sun hits the side of the trailer, warming the air in the trailer. The colder (maybe upwards of 50 degrees colder) snow & ice on the room temperature is fairly effectively transferred through the roof skin of the trailer, so the saturated vapour pressure is exceeded where the warm/moist air contacts the cold roof metal... moisture condenses on the roof and commonly (as I found), it basically rains inside the trailer, on a clear sunny winter day. I'd guess so-long as the vents could keep the inside temperature similar to the roof tin temperature or keep the inside below freezing on clear sunny days, that should diminish or eliminate the possibility for inside roof sweating. Parking the trailer in the shade, so the sun can't get to it on sunny winter days, seems to help too. Removing the snow and ice from the roof before the sun comes out seems to help too. I still tarp my stuff in the trailer... just in-case.