A search warrant was signed by a magistrate on the basis that a CI told officers that her roommate's boyfriend is a drug dealer. She described where the marijuana would be found in the house and told police that she had heard boyfriend speak of drug deals.

The CI has never before provided information and police did no independent investigation to determine the CI's reliability. Instead, the police relied on the CI's good standing as a university student, her gainful employment for some time, lack of criminal record, and participation in church activities as information tending to corroborate the CI's reliability. A magistrate signed the warrant and the drugs were found precisely where the CI described they would be.

I am facing a challenge that the information stated in the affidavit is insufficient to reach probable cause. All the cases I've looked at tell me this is probably the case.

Has anyone dealt with this issue?

Isn't your situation akin to an identified member of the public as opposed to an anonymous informant? More importantly, you are dealing with an identified citizen of good standing versus a typical "criminal" informant working off cases. So, credibility should not be a problem. As long as you have basis for the knowledge--I saw him with what he said was marijuana--you should be there.

Doesn't the law distinguish between Rufus McNasty, the ne'er do well ex-con who Officer Flatfoot popped for possession versus Jenny Dogooder, the concerned citizen that walked in to report a crime?

Apparently, courts do distinguish between a citizen named in an affidavit and a citizen who's identity is being withheld. All the cases I've looked it indicate that courts require some sort of corroboration of the CI tip in these kinds of cases. All I have is that the CI, who's identity was withheld, is a good citizen. Does anyone know of a case that has survived suppression in such a scenario?

Isn't the question identifiable rather than identified? You don't have an anonymous tip, you have someone who identified herself to the police and put herself in a position to be held accountable for any false statements. That the police chose not to name her on the affidavit doesn't do anything to impact her credibility.

Tom Bridges and Ted Wilson, Warrants Manual for Arrest, Search, and Seizure, (TDCAA 2009, 3rd Ed.). It discusses the difference between confidential informants, usually criminals themselves, and "disinterested persons" at pages 81-83. The affidavit you describe makes me think your affiant has the book.

Cook v. State, 497 S.W.2d 295 (Tex. Crim. App. 1973) (affidavit contained PC where is stated "MY SOURCE DOES NOT HAVE A CRIMINAL RECORD AND IS HIGHLY THOUGHT OF BY THOSE ASSOCIATES CONTACTED. MY SOURCE IS GAINFULLY EMPLOYED IN A LAWFUL LAW ABIDING OCCUPATION AND FOR THESE REASONS I DO NOT DESIRE TO NAME MY SOURCE. MY SOURCE HAS NOT GIVEN INFORMATION IN THE PAST, HOWEVER MY SOURCE HAS PASSED ALL REQUIREMENTS OF RELIABILITY IN THIS OFFICER'S ESTIMATION.");

Mueller v. State, 202 P.3d 404 (Wyo.2009) (persons unnamed in warrant affidavit were "citizen informants" entitled to "a presumption of reliability" where, as here, their identities were known by the officer who obtained the information from them).

Lueptow v. State, 909 S.W.2d 830, 832 (Tenn. Crim. App. 1995)("when the information is supplied by an unnamed citizen informant, as in this case, it is presumed to be reliable; and the state is not required to establish either the credibility of the informant or the reliability of his information.")

You might also look at LaFave 2 SEARCH & SEIZURE § 3.4(a).