By our calculations, you should look at sowing Veilchenblau about 35 days before your last frost date.
‘Veilchenblau’ is German for ‘violet blue’
‘The Blue Rose,’ ‘The Blue Rambler’
1 Old Garden Roses and Beyond entry on Veilchenblau http://www.rdrop.com/~paul/climbers/veilchenblau.html