No, SatoshiDice is not 100% on the blockchain, as it uses their own odds generator to determine who wins or loses.

https://en.bitcoin.it/wiki/SatoshiDice (Random Number Generation section).

Our game relies simply on the last transaction to enter the next block to determine the winner. No external information other than what's on the blockchain is needed to play the game, and at any moment, one can visit https://blockchain.info/address/1RaceBKYh5saS5D54vbNzPrLjWENviBMR to see the past winners, past prizes, current players, current game state, etc. 100% on the blockchain. That's what this game is