I bought a set of Cyclops rollers a few years back and it was scary to say the least when I started riding on them.
I too was trying the door-frame technique, but I felt it to be dangerous in case I fell and could not grab onto the door frame in time!
So I simply watched a few videos on YouTube and learned the best way was to start riding with the rollers next to a wall, with about 20cm gap between the edge of the rollers and the wall.
Next I placed the bike onto the rollers but leaned it downwards towards me, so I could saddle my left leg (assuming wall is on your left) over the bike. I then clipped on my left foot first and whilst holding the breaks firmly in place, I sat myself up and clipped on my right foot into the last pedal. At this point I am actually leaning against the wall slightly.
With my left hand on the wall, I started to pedal (yes, set the gears to low resistance before starting, so you pedal with high cadence).
This is the point of no return.
Let go of the wall! And do it sooner rather than later.
Quickly place your hands on the levers as you would normally and look over the front wheel.
You will naturally balance as you pedal.
After a while you'll get used to it and think, why were you so scared trying in the first place!
Some guys on YouTube can do amazing things with rollers, riding one foot, standing on seat, etc. I wouldn't dare!