I was able to get all the stunts for this achievement by bunny hopping the SUV off Cowell's Tower (see any of the guides in Front Flipper for more details), except the long jump. For the long jump, I give the props to Kojiiriin. I just want to give a few more details about it.
The tunnels he's referring to are the tunnels out of the Agency Tower (#1 goes toward Los Muertos, #2 toward The Volk, etc.). For the long jump, go down tunnel #1 with the SUV. Try to keep the speed around 170 MPH until you get to the red marks on the ground near the end of the tunnel or you'll come off the ground at this point and you won't get a good bunny hop at the end of the ramp. Just as you hit the red marks, begin fully accelerating and charging the SUV's bunny hop ability (by holding the B button). Release B just as you exit the ramp, and you should go flying just as he predicted.
Regarding the ramps in the arena for barrel rolling, I tried and tried to get them there, but either I couldn't get enough speed to complete the barrel roll, or I would hit one of the rafters. I tried the agency supercar and the gang cars that were around the arena. If anyone has been able to get a barrel roll there, I would love to know the specifics on how they got it.