In most casino table games when you buy in you are given chips (technically called checks) that have cash value, they generally come in color and denominations of; White $1, Red $5, Green $25, and Black $100, depending on the amount you buy in for the dealer will give you chips accordingly.
However, unlike the other table games, when you buy-in at a roulette table, you get your own colored chips; these chips have no cash value and are used for play only at the roulette table only. They have no denomination imprinted on them and each player gets their own color.
This is done so there is no confusion of which bet belongs to which player, since each player has their own color, usually pink, light blue, light green, orange, light red, etc. They are usually very colorful chips and quite different from the standard chips (or checks) with the dollar value imprinted on the chips.
The denomination or value of the chip is determined by you. When you buy in you tell the dealer what denomination you will be playing ($1, $5, $25, etc.). He then places a chip of your color on the side of the wheel with a marker identifying the denomination you are playing.
The croupier (or dealer) will pay your winning bets with the same color of chips.
All of your chips have that same value, when you are finished playing, the roulette chips are then exchanged for real chips (or checks) that you can redeem for money at the cashiers cage.
Know your play. Know your way.