I agree that asking if you want flowers is not a romantic.

However, I think that in the future your response should be “Yes I would love to have flowers!!!,” with the intention of teaching him or reinforcing in him what makes you happy. And then, if he dutifully gets the flowers, you make your honest feelings about flowers known with a lot of affection.

(Now that you’ve told him that you don’t want them, though, he might need to be reoriented in his thinking. You might need to go out of your way to let him know that truly you do love flowers.)

Hopefully, he will gradually catch on over time—so that he can at least say to himself “I don’t understand flowers but for some reason they make my hopefullylost1211 really happy so I’m going to get them for her.”