I'm building a strat with swamp ash body + rosewood neck and i'm afraid that the tone might be too bright so i wonder if there's a tremolo bridge that can add warm and sustain the the tone?

With a rosewood neck, assuming you mean the actual neck and not the Fretboard (hoping because that would be awesome to see), the guitar will not be bright. However, going on the idea you probably mean the fretboard, a bridge really isn't gonna add any warmth to your guitar. Look for some nice warm pickups to go in it, that's the best advice I can give.
yeah it's rosewood fretboard sorry.

I thought the saddle's material would have great influence on tone thus the difference between floyd's, wilkinsons and kahlers but thanks anyway, pickups do really have greater impact.