I want to use an oil base Polyurethane on my natural red oak to pull out the richness of the wood, but I'm uncertain as to what brand to buy. I want a high gloss finish and would like to know who do you prefer and why. Also, what applicator do you recommend? I have finished a bedroom with Varathane with a wool applicator, but wasn't impressed. I can leave the house after applying so time isn't an issue.

oil based poly is pretty simple so there isnt a huge difference as long as you are buying a professional grade one. I personally like bona woodline, lenmar and polo plaz. depending where you are some might be more readily available than others. I would recommend rolling any of these with a small nap 5/16 or 1/4 nap roller. Just let the finish work dont try to level it or over work an area thats starting to set up. put it down at 500sf per gallon and you should be good. thin to win is my motto, three thin coats is twice as durable as two thick coats with the same build.

Roller? Would that not create bubbles?

depends on the viscosity of the products. all the aforementioned have a pretty heavy body and long flow/open times under normal conditions. The temps and r/h need to be normal, 60/70 deg and 35/45 rh is what is ideal. dont put cold finish on a hot floor and vice versa, cut off all direct sunlight and forced air. if you are timid try it out on your first coat, if you have issues you can screen it out before the next coat.