Seth Meyers -- Just GUESS Who's Playing Paul Ryan on 'SNL'

Seth Myers tells TMZ he's already taken himself OUT of the running to play Paul Ryan on the upcoming season of "Saturday Night Live" ... insisting the identity of new Paul imposter is a closely guarded secret.

Myers -- who's the head writer on the show -- was walking his bike in NYC this week ... did drop one obvious nugget, we're DEFINITELY getting a Mitt Romney sketch on the season premiere.

1) Bill Hader
2) Taran Killam
3) Bobby Moynihan
4) Jay Pharoah (Um...)
5) Kenan Thompson (Yeah...)
6) Random new guy (crap shoot)

Choose wisely Seth.