[MT-AU Public] OSPF with backup paths

Hi all, Hoping somebody can offer a suggestion here. We run a number of sites with a single fibre back to our DC, we have a virtualised redundant core network there and want to take the fibre vlans to each core router for termination rather than just one so that we have redundancy in the core. We have a /30 going from each site to each core router and OSPF running at both ends. By using OSPF interface costs in the DC we can preference the traffic flow through one core router or another, but when there is only one interface at the remote site what's the options for preferencing that traffic flow coming back using OSPF ? Any suggestions would be appreciated. Thanks Paul