For your 2022 Forest River Rockwood I recommend going with the Furrion RV Tankless Water Heater - Gas - Automatic Pilot # FR98SR.
This is a tankless unit measuring 12-5/8" wide x 12-5/8" tall x 19-1/4" deep so you won't have to do any additional cutting to make it fit, has a heating capacity of 13,000-60,0000 BTU, and will work in elevations as high as 4,500 ft. view full answer...