...**long whistleeeeeeeeeeeeeeeeeeeeeeeeeee**...um...ok **rolls up sleeves**
A secondary beam half way up (down) each rafter, and a post on each end and one in the center holding it up (however I assume you would have issues with this method...since there would be a post in the middle of the floor).
A Glu-Lam or LVL engineered to span 20 unsupported feet in the same location described above with a post only on the ends.
Sister a 2 x 6 on each side for at least 4 or 5 feet above and below the original splice. (To do this, the original rafter would have to be jacked up in such a way to allow attaching these 2 x 6's on each side while it's supported in the correct position)
Similar to above: Sister a full 20 foot 2 x 6 onto each existing rafter (basically a new rafter without removing the old...these would obviously have to be cut properly on the ends to work correctly)
Order 16 (for 16" centers) or 11 (for 24" centers) trusses and replace the entire roof system. (I know, I know. I'm just throwing out ALL the options I can think of)
Live with it. (but keep a CLOSE God....blessed eye on it if you're going that route)
I'll keep thinking...and I'm sure someone else has ideas different from (and probably superior to) mine.