While Rosario+Vampire is a an alright manga, it hardly qualifies as romance. More harem than anything, what with the gratuitous amounts of fan service.
One manga I would suggest that hasn't been posted would be Yume de Aetara. It was in Business Jump but it's balances comedy and romance pretty well. It's a refreshing to see romance play out that doesn't take place in high school and its interesting to see the hardships a salary man goes through just for love.