Having romance can and will add some much-needed spice to a rather drab roleplay. That being said, if the general idea of a roleplay is not centered around romance, then adding it can be unnecessary and disrupt the flow and storyline. Similarly, a roleplay [i]only[/i] about romance, be it straight up smut or a story about high school lovers, can also grow stale rather quickly. That is, if the romance is mainly superficial. It's much more interesting to add depth to it, because love is not a shallow emotion. If this level of profoundness can be achieved, then the roleplay can be very, very enjoyable. Unfortunately, it's difficult to go too deep in a large, group roleplay, so I think this can only really work out nicely in the 1x1 section.

I'm not self-advertising here, but I had a 1x1 roleplay with a friend here. The characters were actually together in an older, group roleplay on the old site, and we decided to do a 1x1 sequel with our characters in college. Sure, some of the parts were sappy or not too original, but to date is has been my favorite roleplay and was the first I've been a part of to have an ending.

So, romance has the potential to make a roleplay great. Just keep an eye on how you play it out, and if it's really necessary.

Saying roleplays should never have romance is absurd. What would the world be without love stories? (And while a roleplay isn't a story per se, it's... kinda the same.)
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I didn't read every single post here, but I feel like I just repeated what everyone else has already said. If I did, then... Oops?