Good advice above. I have a stepstool adjacent sometimes, other times I use the wall.

I set up my rollers in front of a window. Looking out is nice, and the reflection is just enough visual feedback of being centered, and puts the eyes out front instead of down.

I build a front-back tracked roller system under the rollers to make it a "freeride" system...once the regular rollers stopped being terrifying. I find it does help with standing without feeling like I'm going to pop the bike over the front roller.

But it turns out that keeping in the 20" ish width while standing is a challenge. I thought I was stable!

Ditto drinking from a water bottle. Scary weaving!

I have crashed. As others mentioned, there isn't a lot of forward momentum. I do think I damaged a spoke as the front wheel went off to the right and bike leaned left and my foot went down. I broke a front spoke the next time out afterwards. That was an adrenaline spike!

[Edit: spike/spoke]