[Win] Certificate Authority gone. Now what...

I tend to a windows-domain with 3 2008R2 DCs and we've just had our Radius-service fail. Long story short, the Certs issued to the Radius-servers has expired ... aaaaand we dont have a CA any more.

At some time during the last year, we dismantled a lot of "leaf"-DCs as we consolidated our infrastructure. The work was largely not done by me, so I cant say for sure what happened to the CA.

What I see now is a typical "domain-host-CA" certificate issued *by* one of the remaining servers *to* the remaining servers, so it seems the CA-role was there.

I have the top-level cert, with its key -- so Im thinking; It should just be a matter of installing the CA-role back on the server which used to hold it, give it the currently valid cert and carry on from there.

Would that work? Whats the pitfalls of installing a CA on a different machine? What would baby sysadmin jesus do?