I've not had it reported yet, but from the code I would expect there to be a problem adding roles or doing other operations on a server started from another machine because the machine key will always be chosen for the ssh connections.
If the machine key that started the server is available we should certainly use that as that is always reliable. If not then we should let ssh choose the key using it's default configuration and if that doesn't work then the relevant ssh key will need to configured on the server outside of the scope of Profab.