Local skateparks?
And there are other ways to get going backwards. From a curb endo, or go down a small hill, or push with your feet until you get going...
THINK! This is BMX, not rocket surgery. You need to start looking at everything with different eyes. Open your mind, if one way doesn't work, try a different way.

And staying on your feet is even better than rolling out of falls. I've gotten rather good at running out of things.
-Bill