Painting, ah, something my wife asks me to do quite often.
You are going to do several bedrooms. That's alot of work.
Rollers: Yes, the extensions for your roller are very nice. They will allow you to stand back, a few feet from the wall, and paint up and down in nice, long vertical strokes. This is far less tiring than standing up close to the wall and have to reach all the way up and all the way down over and over.
Bucket for rollers: skip those roller trays you see. Buy a 5-gallon bucket and a metal screen to fit on the outer lip of the bucket (to wipe the excess paint off your roller). You can get more paint in a 5-gallon bucket than into a roller tray, saving time. With roller trays, you'll have to stop and pour paint into the tray way too often.
Brushes: You'll want to do your edge work before rolling. I have switched to doing most of my edge work by hand. I do use blue tape to tape around baseboards and molding. But you still can't slop a ton of paint up against the blue tape, because some paint may bleed underneath. If the walls are to be a different color than the ceiling, and if you don't have crown molding, I like to use an angled trim brush and paint the edge freehand. If your hand is steady, you'll get a nice, clean edge. Look for an angled Purdy brush, perhaps about 2" - the Purdy brushes are excellent quality. I don't care for the edging tool that you mentioned - I tend to get paint on the little wheels, and then I have to go back and clean-up.
You are saving alot of money if you do this paint job yourself. So I agree with many of the comments made above - buy only good quality paint, don't chintz on the supplies, and you will get better service at a local paint store. Buy quality brushes. You didn't mention it, but I will often go up on the paint sheen. Flat paint is harder to clean than a satin or semi-gloss (especially in childrens' rooms). Be sure to keep some paint when the job is done for touch-ups later, and label each can so you know which is which.