Now that Mother's Day is past, flowers are once again a reasonable price. I refuse to get caught up in the commercialization of holidays. I can give my sweetheart a dozen roses once each season for the price it would cost me if I purchased them on Valentine's Day.
You can probably find some roses just begging to be bought for a few dollars. It doesn't matter if they are wilted. You are going to use the petals only.
Make a trail from the front door to the bathtub and have some petals floating in a hot drawn bath, surrounded by candles for your one and only to greet her (or him) after a long day or week of work. It's inexpensive and quick, but after all, it's the little things that count.