You could rent a boom lift, but this is expensive. You have a couple of options other than the boom lift;

1- Extend a long ladder up the roof (same angle) and work of of it, like stairs. This might work if the height isn't too much and you have or can rent a long enough ladder.

2- Use a safety harness attached somewhere to hold you and your tools. I have done this but it isn't easy or fun.

You will have to be inventive without being dangerous.