Rossi is last documented in Mantuan court records around 1628. No source names a date or cause of death; he disappears from the record along with his sister Europa during the 1630 Austrian sack of Mantua and the plague that followed it, either of which could plausibly have killed him, and neither of which is confirmed to have.
What would resolve this A burial record, a parish or ghetto register entry, a will, or a documented later sighting of Rossi in Venice, where some Mantuan Jewish refugees are known to have fled, any of which would fix either a date and place of death or evidence that he survived the sack.
OpenArchival research, Italian Jewish history of the War of the Mantuan SuccessionWikipedia contributors, Wikipedia, "Salamone Rossi"