The best (IMHO): 2 piece Z-bracket, similar to that of ColoNative but a 2-piece. One piece of alum angle is bolted to the panel bottom, another piece is bolted to the first piece back to back, to make a Z. Adjust it to height by drilling the hole (between two pieces) where needed.
The easiest - buy a 2-piece Z-bracket online (don't remember where, google it up). Though they are often mere 1/8" thick (you might need 1/4", see notes below), with inadequately small footprint, and only one bolt holding 2 pieces together.
The foot of the lower bracket is attached to the roof with 2 or 3 sheet metal stainless screws #10. 3 screws if you don't hit the rafter, 2 screws if you use 6 brackets per panel vs 4 per panel. Put plenty of Dicor self-leveling sealant under the brackets and cover the screws heads as well.
I designed my system to be tiltable and used single-piece alum angle bolted to the side of the frame - not to the bottom. Into the frame I installed stainless rivnuts, so that the locknut under the frame becomes unnecessary.
Tilt is not as popular as it used to be, because panels are cheap and you can get more wattage instead. I would not bother with tilt, considering 750W array in CA.
AM Solar products are expensive. Have a look at their single-piece brackets in the link above, to get an idea how a Z-bracket looks like - and then make it RIGHT, of 2-pieces.
Sometimes brackets have to be 4"-5" tall, to clear plumbing vents - in this case, and considering monstrous size of 250W panel, I used 1/4" thick alum angle.
Places like
onlinemetals.com will sell you any size and any length alum angle and will cut it for you for a nominal fee.
EDIT:
You failed to mention but it looks like your "RV" is a motorhome. On a of motorhome the shape, placement and attachment of brackets to the roof becomes quite different. In this case, disregard 60-70% of the above info, including mine.
