I'm sure plenty of people will post on the warranty issue. As my "guess" would be, IF the dealer/Ford can confirm any issues come from you adding the lift, then the parts affected would
not be covered under warranty.
On to the next part. Don't know about the rough country lift, but I did help the brother in law install the zone offroad 2" level lift on his Big Bend. It was a pain, but in hindsight, once you get 1 corner done, you then know the correct way to do the other corner and it goes much smoother. Anyways, he likes it, put 295's on his Bronco. We removed the crash bars to be safe, you'll definitely need to remove for 35's. And will of course need an alignment done.
Keep in mind, not many people are fans of spacer lifts. They are cheap, but at the same time could add to potential suspension problems down the road.
https://zoneoffroad.com/products/2-in-lift-kit-bronco-2021-ford-bronco?variant=39806916427864 2021 Broncos - BaseSquatch 4dr. Rapid Red V6 Soft Top
Big Bed 4dr. AMB V6 Soft Top Tow (BIL's)
Nitto tires SUCK! You've been warned.