Here is the announcement from their website:
We're currently experiencing a temporary website outage due to Rootsweb hardware failure. Rest assured, our development and web operations teams are busy working to securely restore the site as quickly as possible.
Our initial expectation is to have the site back up and running on or around March 15, 2016.
We apologize for the disruption and thank-you for your patience. We will provide other updates here as we have them.
Patience is definitely required! Fingers crossed that Ancestry.com can get this solved and that Rootsweb will be back with us in another couple of weeks.