I don't do roses, so someone else will have to help you there, but in my Japanese iris beds I have daylilies, siberian irises, ornamental grasses, and I just love groundcover geraniums around the feet of the JIs. I have Biokovo, Karmina, and Bevans Variety geraniums.

Thank you for responding with specifics on the geraniums. I will definitely consider those. Do you have a good source for those? I am also intrigued by the ornamental grasses. Can you suggest some non-invasive ones that are not too big?

I'm sorry. I have a nursery, and really don't know the best places to buy geraniums retail I'm sure someone else will help, or maybe ask over on the geranium forum.

I love the smaller miscanthus, as far as grass goes to combine with beardless irises. Or maybe a pennisetum.

At first I thought that roses wouldn't like the conditions that JIs need, but aren't they supposed to like watering from the base and not on the leaves? Or do they need to dry out between waterings? I don't know roses. Rose blossoms are gorgeous, but the plants just don't have a chance under my care.

I wish I could offer some suggestions for companions, but I'm so enamored by irises that I don't need anything else. Anything planted with an iris is just a distraction and something that could have been an iris in my eyes and garden. ;)