I am going to be building a roll in for my dirt jumps this summer and iv never done it before and looking for some measurements and angles that work well.
It has to be big enough for a jump thats about 4.5 feet tall with a 13 foot gap.
angles depend on how far away the roll in is from the take off and how high you are willing to make your drop in. A lot of dirt jump building is preference though. if you wanted to make a wood drop in try looking at plans4ramps.com theres some good ideas there
Consider adding a roller or two before your first lip for additional speed.