Spend the money on St. Anthony repairing it instead. IMO, I think that the addition of a traffic light at the end of the ramp where NB 23 intersects St. Anthony to control exiting traffic and traffic entering the NB ramp is all that's needed. Few vehicles continue on EB St. Anthony whereas most turn NB on 23. The truckstops on the west side of the interchange cause the congestion and installing lights with actuation strips in the truck stop(s) driveway aprons would eliminate most of the issues, at a much reduced (financial) cost.
I've never expected much as far as common sense from traffic engineers.
Roundabouts are fine in a rural, low traffic setting. That isn't what this is.