search, no warrant Arrest, Search, Seizure, Warrant

quick story.

Problem: My home was visited and subsequently searched yesterday without possession of a warrant(we did not ask to see one; nor was one shown). Found inside the home by the perpetrators were a gun, marijuana, and some e-pills.

My roommate, in fact, is a drug dealer BUT there is no record of that on file.

The situation: My roommate is a convicted felon (convicted of a non-drug related crime) currently on parole. His P.O. and several other officers asked to speak with him; naturally he consented. Once inside the house and without announcement the officers began to search the house.

The question: Can a parole/police officer search, without presenting a warrant, a house based solely off suspicion of possession of drugs?
Similarly, even if someone told the police about his activities, do they still hold the right to search the house???

Thank you

Humble