Reward Flight Query

We are Red Status with two companion vouchers and 100k points. We would like to book PE flights from MAN to LAS, then MCO to MAN. My question is please, can we book the outward flight as one way then when the return becomes available book that too using our companion voucher and points? Would we need to use the two companion vouchers, or would Virgin change the companion voucher to a return rather than one way. We have fixed dates on the outbound flight and I know the MAN to LAS is a very popular route.

You can book one way and then add on later, I did it recently

You only need 1 voucher