Okay so he buys her flowers. Whatever. They're flowers, they don't mean anything. Technically they're dead. They're dead plants. If he was giving her chocolate, then there would be something to talk about.
Rachel throws her arms around him and kisses him soundly when he hands the stupid roses with a gruff "here you go." The smile on her face and her tongue in his mouth convince him that maybe this wasn't the worst idea, even though it's totally emasculating and honestly, so Finn-ish of Finn to suggest.
Still next time they fight, maybe he'll bring her chocolate and her dads won't be home to death-glare him into submission, and then they can get freaky on the couch.