Probation is a second chance from the court. You agree to follow the rules and the judge agrees not to give you the maximum sentence. If you don't follow the rules, the judge can sentence you to anything up to the maximum for your offense.
You're the one on probation, not the other people. If guns are found in the home, you're the one who's in trouble, not them (assuming there is nothing else making it illegal for them to have the guns).
People on probation often have a search clause, which lets the police or probation department search their homes and cars for evidence of probation violations. If you're on probation with a search clause and nobody else in the house has one, then the cops can search any common areas of the house.
If the other people in your home have guns and it is illegal for you to possess a firearm, they should keep the guns in a locked gun safe in a private bedroom, preferably one that has a lock that you can't open. If your housemates don't care enough about your future to lock up the stuff that can get you in trouble, find another place to live.
Please understand that this is a general discussion of legal principles by a California lawyer and does not create an attorney/client relationship. It's impossible to give detailed, accurate advice based on a few sentences on a website (and you shouldn't provide too much specific information about your legal matter on a public forum like Avvo, anyway). You should always seek advice from an attorney licensed in your jurisdiction who can give you an informed opinion after reviewing all of the relevant information.