Yes. Quoting the license agreement:
You may run, at any one time, one instance of the server software in one physical or virtual
operating system environment on the licensed server.
So your "Standard" SBS can be installed on a Hyper-V Server (note that I said Hyper-V Server, which is a free product from Microsoft; it is not part of or on the SBS DVDs. You have to download this separately from MS).
Because Premium Edition is designed to run on one or two servers, you may separate the server software and run one instance of each of the following components in one physical or virtual operating system environment
The "Premium" server can be another VM on the same Hyper-V Server, or at your option, on a physically different server, including running on that server's bare metal or as a VM under a hypervisor (such as the free Hyper-V server mentioned above).
You may not install a Core version of the SBS server, add the Hyper-V role, then create two VMs within it for the "Standard" and "Premium" SBS servers.
From a technical standpoint it's a good idea to separate the roles into at least the two VMs. Most modern hardware can easily handle running two VMs, though it typically needs a bit more RAM and HD space. CPUs are rarely a bottleneck these days.