Are you looking to acquire roulette chips for poker purposes or roulette?
If it's for roulette it's fairly simple. Each player needs their own color. A busy table in a casino is 7-8 players. Any more than that and it really slows the game down so the casino will open another table. Hence for true roulette chips you'll usually find only seven or eight color possibilities. The number or letter on the chip only matters if you run multiple tables.
100 chips per color is the bare minimum. I have 160 and find it works well for casino nights. I'm not sure how many
@T_Chan has but he also runs roulette at some of his events. I think I've seen pictures with him in the 200s.
Players buy in with a barrel at whatever denomination they want and that leaves me with 40 to handle most payouts and still have a full rack of each color on the table. Casinos will sometimes have 300 per color but given the table layout that requires a full size wheel. If you go with the more common consumer sized wheels (18-22 inch) you'll run out of room trying to arrange stacks around the wheel.
What if someone puts a full barrel on a number and it hits (35:1), you ask? It's extremely rare but when it does I just pay the player directly in value chips.
In sum, for the average casino fun night setup 100 chips per color is the minimum, 140-160 is ideal and 200 is way more than enough.