Depends on how short and steep the hill is. If I can motor over a hill by standing without shifting or losing speed, I'll do it. Otherwise, I might drop down a gear and spin up while seated. Different things in different cases...and that's just me. You'll find that a lot of people will have different ideas on this, so try it diefferent ways and see what works best for you.

I would say that you will likely want to shift your weight slightly forward when out of the saddle. I find the most stability when I center my weight evenly between both wheels, again depending on the grade. For steeper sections, more weight on the back wheel, but still forward of the saddle. You want to keep enough weight on the back to maintain traction, but without lifting up the front wheel. If all you have are little rollers, though, this shouldn't be an issue for you.