I genuinely think roman (pretends and says he) doesnt care too much about valentines day and how much he cares or plans is based on his partner if he has one.
Do they want this huge display of affection? Easy, 1000 roses in the penthouse and he rents out a space in timesquare to show a picture of the two of you. Plays it off like a royco valentines play "showing the peons what theyre missing by not being on our side"
Do they want something small? Well small is hard for Roman and the necklace he might get you is worth the down-payment on a house, but its small isnt it? Has whatever your favorite food is waiting for dinner whether its take out or his staff put it together. Its your favorite and it "wasnt a big deal. barely a favor."
But I think roman wants to come home to his penthouse and see that you have something for him instead because it'll be something from you and your heart (probably) without ulterior motives (expect maybe getting in his pants?) he barely murmurs a thank you when he kisses your forehead, but he will never forget the way he felt coming home to flowers and a 10$ box of chocolates from you