It can be intimidating to deal with the police. If they ask to search your home or apartment, you may think you have no choice but to say yes.
This isn't true. You do not have to consent to a search if the police do not have a warrant. They can ask all they want, but you can say no.
Refusing the search isn't just an option that you have; it's a constitutional right. It's a fundamental part of the American justice system. No matter how the officers treat you, they are not above the law. They are still governed by the constitution. You can use your rights and you should stand up for them if they're in danger of being violated.
Plus, refusing the search actually helps you if the police do it anyway and find evidence.
For instance, maybe they're looking for drugs. They have no reason to believe you have them and no warrant, but they're hoping to stumble across something.
You refuse the search, but they force their way in and do it anyway. They find marijuana in a cabinet in the kitchen.
Unless they can prove that they had a compelling reason to carry out a warrantless search, that evidence can't be used in court. You don't have to prove that you didn't know it was there. It doesn't matter if it was yours or your roommate's. They cannot use it because they only found it by violating your rights.
As you can see, it's important to understand all of your legal rights, both before you've been arrested and if you're facing charges.
Source: Huffington Post, "5 Reasons You Should Never Agree to a Police Search (Even if You Have Nothing to Hide)," Scott Morgan, accessed Nov. 02, 2017