I'm finishing my basement and had a question about installing an exhaust fan in the bathroom. Can I tie in the exhaust fan ducting into the vents from the bath fixtures, which will exit out the roof. Air and odors would exit out the roof and any moisture should flow down to the sewer lines under the floor? I understand that it should go out the rim joist to the outside but I was just curious.

Never mind, this wouldn't work because it would give sewer gas a direct way into my home. Duhhhh!!

Ahh! You answered your own question. That makes you a expert. Welcome to The Plumbing Page at vAMHD. Cheers, Tom

Just for laughs. I saw a house last week that had the basement bathroom exhaust tied directly into the return ductwork of the forced air furnace. I guess they wanted everyone in the house to enjoy the aroma..