The resistance of a roller set varies with gearing. Magnetic and fluid resistance units vary the resistance with speed of rotation. On my set, I have the usual road effort at the usual road speeds on the flat. Thus in my biggest gear at about 35 mph I've maxed out the unit. I don't think I can hold that for a full minute. Staying upright is not an issue for most riders. I've taken the resistance unit off and hit over 40 on them, but I only have 52 X 12, so can't go really fast.

Easy peasy refers to staying on the rollers at normal speeds and resistance in a doorway, which in fact it is. I don't recommend standing sprints until one has a lot of experience on them.