Do you have to sell everything on the floor?

Actually, a lot of roguelikes do have towns or stores. The original rogue did not, but it initially split to into four major branches: moria, omega, larn, and hack/nethack. All of those have towns or stores to sell and buy items. Then the dozens of variants which also carried over the stores. In fact, outside of rogue, i cannot think of any that do not have a town or store to sell items. I think you mentioned crawl, which I admittedly have not spent much time with.

 

Well I said towns, not stores. Stores are in almost every roguelike, including later ones like crawl. But you weren't really encouraged to run back to them all the time, they were often just places you ran across once and moved on.

Not that there aren't roguelikes with towns of course. Most like TOME or ADOM though have some form of mechanic that discourages you from running back too often. In the case of ADOM they punish you pretty severely for wasting too much time, in the case of TOME you get an item that autosells your stuff for you.

I'd recommend trying crawl if you haven't, it's an incredibly well designed game. Although I do find that I get bored of it if I have a character that survives for an extended period of time (not something that happens very often).