There are 2 different gang charges. Rodriguez deals with the charge of being a member of a gang holding that you cannot be so charged if you acted alone. The gang enhancement is not affected by Rodriguez. For the enhancement to apply you simply have to commit a crime which somehow benefits the gang. Sounds like your husband was convicted of the latter so no sentence reduction would be possible.
On the face of your question, John Kaman's answer is correct. However, there may be more facts that otherwise allow a challenge to the sentence or your husband's confinement. When the basis for the confinement is legally improper, such as due to a constitutional error in a ruling during trial, a writ of habeas corpus may be an option. Since your husband was convicted three years ago, there may an issue of whether such a writ is barred. I would speak to an appellate attorney to clarify what options your husband has, if any.
I agree with both of my colleagues. There might be some additional facts that might give grounds for post- conviction relief. Speak to an experienced criminal defense lawyer about your options.