I did a bit but after contemplating I do not think it is 100% provably fair.
I have no control of the exact time I am sending to you to create the hash.
You can also try 4-5 hundreds of the second around the time I sent you and to pick a losing hash for me.

Do I miss anything? I guess I need to change my secret before every roll in order for it to be truly provably fair, right? And you not use the time, too.