Wow! What a trip he's putting on you. I don't know if you can let someone like that down easy? Can you move across country? :-) I was fortunate that I was that far away from someone who "married the first person he kissed" (am I so glad I never let him kiss me!). I have a girlfriend and she had a guy who got serious, all alone, fast, and was looking at houses to buy for them to live in after they got married and they'd only had a couple dates!

I would just be sincere? Tell him the roses were lovely but you're not "ready for that kind of relationship right now." Make it look a little bit like your "fault" (you're not ready for the relationship) by using "I" statements rather than telling him he's over the top and hopefully he'll get the message?