Depens on his aler egos. If he wasn't an alien I'd Think he has multiple personalities.... anywho when hes a dude, he likes girls. When hes a girl he lives boys........ he's complicated. I'd say it DEPENDS ON WHICH PERSONA HE IS :)
In certain episodes it actually calls Roger Smith "pansexual" Which basically means te go for anything, male female, trans. any gender. I am pretty sure this is spoken around the twelfth episode of season 7. Your debt your life, which is when Roger is replaced.