Radiant Office isn't that strong on romance, but it's really good anyway.
I would recommend:
Another Miss Oh
Witch's Romance
Drinking Solo
It's Okay, That's Love
Queen In Hyun's Man
Splash Splash LOVE (short 2-part drama, but very very good)
I'm more wary of recommending those, but they might be worth a try:
Madame Antoine (the rom-com aspect is good, but overall there's something missing in the plot, but it's still entertaining)
Big (interaction between the MCs is perfect, but the plot gets seriously wonky half way through)