Legal Question in Criminal Law in California

Typically, yes. Police conducting a legal search are not supposed to ignore evidence of crimes committed by third parties. But if the search was conducted in a way that violated your rights, you may be able to have the evidence excluded from court. You should consult with a criminal defense attorney near you asap.

Good luck.

Yes. When YOU have a 4th Waiver, any roommate, spouse, etc that lives with you risks arrest if contraband or illegal activity is discovered during search of 'your' residence or space. Prosecutors would have to show the roommate had knowing possession,, or was a conspirator. But the roommate would get to make all those arguments in court, after arrest.