this sounds interesting! think I will give it a try. do you brine the roast first? As far as the indirect heat goes on a grill, are u saying wrap the roast in tin foil or place in a tin baking pan thing and then get the grill down to 200-225*? how long would u estimate it takes to cook on the grill like that?
I don't brine although you could, I just never have.
If you're cooking on charcoal, I'd lift the grate and move the coals to one side. Wrapping in foil or tin baking pan doesn't matter much, whichever you've got handy. If you're cooking on a gas grill, turn OFF at least 1 zone and using the top rack wouldn't hurt either.
Regarding time, I put 130 degrees specifically because I use a meat thermometer exclusively, no guessing. Depending on how big of a roast you're doing it's 20-40min once you are down to the low-temp portion of cooking.
DO NOT go lifting the grill hood/cover every 10 min and slicing the roast during the low/slow period to see if it's done yet. Stick the thermometer in and leave the doggone grill closed.
Anyone who touches the grill/oven door other than the cook should be subject to having their fingers slapped, with a ball-peen hammer. The cook had better have a good deliberate fuggin reason to be opening the grill/oven or they need to be replaced immediately and mocked repeatedly.
If you do this and your's doesn't look like the pic KurtR posted above, you screwed up somewhere, Kurt's is perfect.