How do I emphasize role-playing during combat?

Right now, the group that I GM for is very, very tactical-combat focused. To some extent, we may as well be playing a dungeon crawl board game for all the role-play we manage.

Now, in and of itself that’s not bad, and I enjoy progressing the story that we’re telling, but I would like more “theatre of the mind” than we’re achieving right now.

The one bit of advice that I always seem to come across is to have the villains and other NPCs in the fight invite role-play by taunting and otherwise engaging in banter with the PCs, but unfortunately I’ve tried and failed at that – largely because quick witted banter is not my forte, and so it comes across as strained and less than engaging.

What I would like are other play-proven tactics that I as a GM can employ to lead my players towards more role-play during combat, without taking them away from their (and my) roll-play comfort zone.