There are lots of tips on rollers out there, as far as learning to use them. I think doorway is a good idea. If you are VERY nervous, have a friend hold your bike by the seatpost as you get up to speed, and once you feel stable ask her/him to let go, but keep hands near your butt to support you if you wobble too much. This allows you to keep your hands on the handlebar.

Look forward, not down. Pretend there is a "finish line" 25m in front of you and ride towards it.

It may take you a few tries but I bet you will get it and start liking it!