What kind of roast? Unless it's a shank, I wouldn't do any sort of slow cooker use at all. I'm presuming when you say coarse grain, it's some form of leg muscle.
Dry brine, yes.....but, definitely calculate it out using a kitchen scale. Depending on your salt preference, 1.5% - 2% of total meat weight (in grams). Kosher salt, sea salt, pink Himalayan salt, it doesn't matter. Just don't use iodized table salt. I love lots of black pepper. Sprinkle with garlic powder and rub it all around. If it'll fit in a gallon ziploc baggie, use that, and toss it around for a day or so. Pull it from the fridge the morning you want to cook it and let it rest for a while. When it's time to cook, pat it dry.
I would reverse sear smoke it. In a 300° grill on offset heat, roll smoke. Oak, hickory, pecan, cherry, or a combination of all those. Don't be afraid to use a temperature probe. I would take it to 128° then pull it to rest. Tent lightly with foil.
While it's resting, stoke your fire and get some blazing hot coals. Put the meat back on there and blast it for about 2 mins per side.
Let it rest again at least 20 minutes. Slice across the grain in thin slices. It would probably go great with a sauteed mushroom & red wine garlic butter.