For your roof vent, I recommend the Ventline Ventadome Trailer Roof Vent # V2092SP-29 which will let the light through and will mount to the roof only. The garnish/trim on the inside is designed for roofs between 1-7/8 and 3 inches thick. I recommend installation kit # 344270KITW for best fit and seal.
If you determine you would like to add a fan, then I recommend the Fan-Tastic Vent Roof Vent w/ 12V Fan - # FV802250 which will fit ceilings up to 4 inches thick. The garnish/trim is... view full answer...