Are you trying to provision VMs through vRA using SCCM 2012 R2? If so you can just use the native vRA integration. Works great. We deploy about a dozen different OSes from SCCM 2012 R2 from vRA 6.2.2. The deployments take about 20 minutes for a fully patched OS. It can take longer if we place it into an OU with additional software packages.
I attached an image of the vRA custom properties im using with SCCM to deploy our systems.
We have a large CM installation so we had to set the timeout of the connection to SCCM from 5 minutes to 10 minutes.