chain derails
 

When I roll my bike backwards the chain derails. .....I can't figure out why.....any ideas?

Because there is no derailleur above the cogs to guide the chain when cross chained. Don't roll backwards when cross chained.

+1

If you roll backward when the chain is fairly aligned (middle of the cassette) it tends to be OK. But without the RD pulleys to guide it, the chain will tend to look for better alignment and shift accordingly.