I don't believe there are any iRule commands to add/delete static routes.. but you could probably accomplish this with a shell script.. though I don't believe you can call a shell script directly from an iRule.. I do remember a post where Hoolio had an idea to log a message then use a custom user_alert.conf to call the script...
Dug up the post here, check it out.
http://devcentral.f5.com/Community/GroupDetails/tabid/1082223/asg/50/aft/814016/showtab/groupforums/Default.aspx
sol5465: Managing static routes
http://support.f5.com/kb/en-us/solutions/public/5000/400/sol5465.html?sr=14786738