Any ideas for companion plants for Dutch iris Rosario?
Perhaps white, cream or soft yellow Aquilegia. Pink Ajuga. Aubrieta - if the pink is not too strident, or the 'blue' a mismatch. Purple or white Muscari. Kniphofia - perhaps 'Little Maid'. Dianthus with silvery/blue leaves. A compatible shade or tones in Ranunculus.
Also grasses, Cistus - if it's hardy in your area. A creamy-white and scented Magnolia. Oriental lilies or daylilies to follow, or tall Phlox.
Poppies. 'Knee-hi' sweet peas. Clematis - either vertical or scrambling. Freesias - if they're hardy for you.