Like most brewing methods, it really depends on what your target/intenetions are as well as how you are brewing.
For full immersion cold brews I have found sweet and chocolate-forward coffees with low acidities tend to brew best when roasted to the solid medium range. Some of my favorites for full immersion brewing has been Guatemalan, Brazilian, Peruvian, and Colombian coffees. I have also found that longer roast times (not only temperature) seems to do a better job of yielding that lower acid cup that still packs a punch with caffeine.
For pour-through brews, like a kyoto style drip brewer, I have been blown away by brighter more acid-forward coffees such as washed African coffees or really high-grown Central American coffees. These types of brewing methods tend to taste best with light to medium roasted coffee in my opinion.
At the end of the day the most important thing is that you are having fun and enjoying it!