I am not familure with TP LINK ER605 so I cannot attest to its capabilities.
If your Rogers Access method is pure fiber then Rogers currently have not finalized how they will distribute Prefix Deligation so on pure fiber all you can get is a /64
If your Rogers Access method is COAX then they are providing diferrent PD all depending on your area. I'm on COAX and I do get a /56 and I am able to populated all my subnets with global addresses. My Router is a MikroTik so it is a very capable device.
So if you are getting a /56 the problem may be your TP LINK ER605 capability or lack of capability.