Toilets have built-in traps and I imagine that the toilet paper holder is hung-up inside it just waiting for a bunch of toilet paper, etc. to clog the toilet with.
You need to try to extract it with a crank-handle toilet auger, or else pull the toilet, turn it over and extract it from there.
Are you sure its a 7 gallon per flush toilet? If so, that toilet paper roll is probably long gone down the drain. If for some reason its still in the trap, the water from the bowl should soften it up enough to flow past the trap on repeat flushes.