Some dummy questions about road/SS builds

1. Most SS or FG track frames are 120mm wide at the back. Most flip flop hubs are 120mm, but some are now 130mm. Check what the Steamroller is. If it's 130mm and your hub is 120mm, you might have enough thread on the axle to just spacer it out behind the bearing lock nuts or put a longer axle in.
   
2. BB usually has a label on the barrel saying what it is i.e. type of taper/spline and width. Just replace it like for like. It should fit in either frame, assuming the Steamroller has a threaded bottom bracket and not a press fit.
   
3. Headsets can be taken out and re-used no problem. Your current one is 1" threaded, however, and the Steamroller looks like it has a 1-1/8" threadless, so it won't switch over. This may mean you won't be able to use your current stem or handlebars if you were intending to.
   
4. Your brake should be ok but you'll only know when you offer it up.
   
   

HTH