I'm not convinced that you need the roller. Caribiners are designed to have rope run through them and it's only one more thing to clog with sand and salt.
I don't think it's a matter of need it certainly reduces wear on the rope, after a seasons use my rope is still pristine. Easy to replace so do I need it...? No... Is there a benefit? Yes.
Mine has never stopped turning but the screw that holds the bearings in place is showing some corrosion. I think I will clean it out and push some grease in there. Either option works great if you are not unhooking. I applaud your innovation in retrofitting for your needs.