This is from memory, and I’ve not used the srbac blog demo so may not be 100%…:
Make sure that "debug" is set to false in the srbac module configuration in main.php.
Assign the "Authorizer" role (or your equivalent) to your administrator.
I think that until those two things are done the default behaviour of srbac is to give everyone access. The answers are in the documentation here - but it takes a bit of digging to find them.