Neither one is correct. It is unclear what you want to say. Your dress is more beautiful than red roses????? You are more beautiful than red roses? (not sure where the 'dress' comes in)

Are you saying you like their dress which is more beautiful than red roses or that you like them more than a beautiful red roses dress?

I like you more than a beautiful red rose dress. I am not sure when you would say that. It seems like It like you more than red roses’ would be more natural.

How about: "Your red rose dress is more than beautiful, I like it!"