oh you never want to bleach rock or anything in your tank, the beauty of live rock is that it has alot of tiny little holes that absorb and provide a home to bacteria , even if you think that all the bleach is out it can and probably will seep slowly over time because its absorbed into the rock, sry to say but i wouldnt use that rockanywhere near my tank and i advice you to not use it eighter
if you do buy dead live rock again , just boil it no need to use bleach
maybe im overrreacting and someone will probably advice you better :D good luck