You can use an unlimited number of ssh keys per user.

On the same account:

Either specify the key for each ssh or scp command:

For Server 1:

ssh -i ~/.ssh/mypvtkey root@pvtserver.com

For Server 2:

ssh -i ~/.ssh/mypvtkey root@officeserver.com

Alternately, create ~/.ssh/config with the following entries:

Host pvt
Hostname pvtserver.com
User root
Identityfile /root/.ssh/id_rsa_mypvtkey
Port 22
Host work
Hostname officeserver.com
User root
Identityfile /root/.ssh/id_rsa_myworkkey
Port 9992

Now, you can connect with: $ssh pvt and $ssh work

You can even do: scp myfile pvt:/root/someplace/