Answers

Roof first, then foundation. (not saying that just because I'm a roofer :)
Gutters are likely involved too.

Fixing the foundation should not undo any efforts spent on the roof and gutters.

All concrete has cracks. The difference is if it leaking or getting worse. Call the local wterproofing or mudd jacking contractor for a site visit.

I jsut had a new house built and the concrete foundation had a settling crack that ran from the casement window to the floor.  THe only way we resolved it was to hire a local basement waterproofing company (Crack-X - Natick, MA.) who utilized polyurethane injection to seal/fill the crack from the floor up to the window.  It was rouhgly $700.00 for the job.  Some DIY Kit info I found useful can be found at website:

https://www.youtube.com/watch?v=dggJsJ2f1dU

Hope this is useful.

Thanks.

-- Jeff

Hire a structural engineer to determine if there is a problem that needs fixing.  If there is he will give you a report and or drawing detailing what to do.  Then call 2 or 3 Class A Building Contractors who are in good standing with BBB, DPOR, have sent you certificates of insurance and current references have checked out. Give them each a copy of the engineers report so they know how to qoute the work and go with the one you feel most comfortable with.  

We agree with everyone that notes to fix your roof first, including any gutters and downspouts. Remember to be sure to run the water AWAY from the home. Water coming down around the drip zone of the foundation is a big problem and can be addressed with those initial steps. Then, you can and should address the foundation with a reputable foundation contractor. Water kills a home. Use the top down rationale and control it. But definitely fix that foundation but after everything above is corrected. Good luck.