Any tips on freezing potatoes? And which varieties are best?

Agree with @Sam1148....only par-cooked potatoes will freeze well. THAT's why Micky D's fries are so good (or part of it....), they're fried at low temp, seasoned, and frozen, then refried to order. Raw potatoes DO NOT freeze well, nor do totally cooked potatoes that aren't in a soupy/stewy sort of dish. Wedges of roasted potatoes, or whole ones, or boiled then diced, then frozen and then reheated are gong to be a mess. The starch molecules will burst upon thawing (and take in the water from the ice crystals) and be a gluey blob.

If you're doing fries. Soak them in cold water. Then dry...blanch them in hot oil a bit lower temp than you'd use for frying them about 325..drain and cool. Shake with seasoned cornstarch in a bag. Lay on a sheet pan freeze..bag 'em up store in the freezer.
Then they're ready for high temp final frying or baking as fries.

I would opt to make your roasted potatoes fresh when you want them. They are quick, easy and so good freshly made. Potatoes last well so I don't see much need to freeze the roasted ones unless you have too many leftovers. I think freezing them causes more problems than solutions.