I would not interplant. The Hellebores would swamp the Geraniums. Use them as a backdrop plant instead.

I'd plant something from the geranium sanguineum line. If 'Rozanne' died in that bed, 'Ann Folkard' won't stand a chance. Likewise, 'Brookside' probably won't do better than 'Rozanne', either.

'Biokovo' sounds like a winner to me. Otherwise, you might try 'Tiny Monster'. I have mine planted in a bed next to hellebores, and Tiny (2nd year down) is pushing 4ft across, 3 times the spread of my largest hellebore. Both of these have sanguineum lineage, and the vigorous root system to get the moisture they need.