There are no minimums when depositing to Rollbit. As long as the network fee is covered you will be credited the remaining amount to your balance.
When you have made a deposit there is no wager requirement on it as long as you have deposited and wagered the minimum of $10 you will be able to withdraw it at any time.
When withdrawing from Rollbit there is a minimum withdrawal size of;
Bitcoin - Amount must be higher than the current network fee
Ethereum - Amount must be higher than the current gas fee
Litecoin - 0.05 LTC
Solana - 0.01 SOL
Rollbit Coin - 1 RLB and on site balance to cover the network fee
NFTs - You need on site balance to cover the gas fee