I finally tried standing on the rollers today during my workout. I just put a little more weight on the handlebars, slowly raised my butt off the seat, and kept pedaling. Only managed it a few seconds at a time, and didn't stand up completely, but it's manageable. I will extend my standing time with more practice.
I mainly wanted to learn this skill to get off my sore butt after sitting in one position for so long. This is the same reason I do a few minutes no-handed each session, so I can relax my arms and shoulders for a while.
Does anyone incorporate standing up into their intervals on the rollers? If so, how? For how long? I have a magnetic brake, so I can crank the resistance up.