Well to refute the 2 above posters I started a work place romance and I have been married to her for 5+ years now.
My suggestion...if you have email to use just send him an e-mail wondering if you could give him a call sometime. If you don't have e-mail then you will have to ask him face to face, but I think you should offer your phone number to him. Basically if he calls then he is interested if he doesnt call then at least you have not spent time wasting on him. "Hey I wanted to give you my phone number in case you wanted to talk or do something sometime." I know if someone had done that with me and I liked her then I would be very happy.
Even though I did marry my wife I would say be cautious with the whole thing, because if things go bad then it can cause a bad work place enviroment.
Start slow. Suggest that you both have lunch or a coffee break together. Then, see where it goes from there. I've had plenty of workplace friendship/ romances... and, I've never regretted one of them. If you feel compelled to ask him out or offer your phone number, I say, go for it... just be prepared for the fact that he may not be as "interested" as you are.
Listen to Ashelen. Workplace romances usually only spell great disaster. Every little up and down will be thoroughly chewed up and spit out around the office coffee pot. Do yourself a favor and let this one be.
I personally recommend avoiding dating someone from your work. It never seems to end well. If you're determined to pursue a relationship with him, you could always jokingly slip the line "It would be great if we could hang out some time...want to exchange numbers?"