Originally Posted by nealtw
The angle braces are there to tie the roof the the floor joists so the roof rafters don't splay out from the top of the wall. Could check with the people at Simpson Tie for a recommendation on replacing them
If the roof rafters are properly connected to the sill plates and/or floor joists, (with the joists properly sized), the floor joists themselves will keep the roof and walls from "splaying out." And before nealtw chews on me, I know that's a big "if." The diagonal braces will certainly make for stiffer connections, but may not be absolutely necessary. Should you choose not to get a local engineer's professional opinion, you could certainly leave them in place. You could even build short kneewalls in front of them, since the space between/behind them is marginal wasted space anyway (but makes a great location for heat and electrical runs, or hiding Christmas toys from the kids).