I found this to be incredibly helpful, more roller manufacturers should include something like this:
With an idea in mind of speed and wattage targets, this allowed me to figure up which size rollers to order and whether to get the fan, 1 flywheel, or 2 flywheels. I used multiple smart trainers with ERG, and it burned me out pretty hard. I’ve been using my crank-based PM for awhile now, and it works really really well.