Caveat: I have not ordered in person, just via Grubhub. I have inspected their web ordering interface as well.
Caveat: I am gluten intolerant, not allergic/celiac, so I'm not 100% certain of safety.
Re: ordering online
Ordering GF online is not as easy as it could be.
Most pastas offered have GF variants that can be requested. But those are not listed when ordering online via their online ordering page or GrubHub. You'll need to call in in advance to let them know a pasta order will be coming in and that you need the GF variant. They are very helpful when you call in, but call IN ADVANCE. If you call in after submitting the order, the preparation is likely to have already started by the time you call.
The ordering pages don't list allergies/gluten either next to the items. You'll need to use the national website's allergy page to understand which dishes are risky. Google for "carrabbas allergy". This is pretty awkward and they and GrubHub could do better in this regard.
GrubHub does not appear to provide a way to add a comment to the order to indicate gluten free or any other adjustments.
My delivery arrived, it included no confirmation that the order or pasta was gluten free. It did include bread. When I called in to ask if it was GF bread I was told it was not. So be very careful. Ask questions. Don't make assumptions.
— Somewhat
— Separate gluten-free menu
— Some
— Excellent