Whoa, fixed gear on rollers - now that is hard core. Much more hard core than I am.
I'm feeling like a bit of a weenie now for finding my lowest trainer gear (34-26 - I have an 11-26 cassette on the trainer right now) pretty brutal on some Zwift climbs. Hmm. I'm still keeping my eye out for the right used bike within my "dedicated trainer bike budget" to pop up on craigslist/ebay/nextdoor, etc etc. Most of what I've seen in my price range has had Claris or Sora, but we'll see - maybe I'll get lucky and someone will sell a Tiagra or even 105 bike for a good price.