Roses are more difficult to germinate than some plants. Try posting your question on the rose propagation and exchange forum. I'm sure you'll get some interesting replies--and probably a lot more questions as well.

I find rugosa seed easy to germinate, but if you want a rambler, you may want to try a diferent line of breeding.

Here is a link that might be useful: Rose propagation and exchange

Most likely that you are trying too hard, and that you are getting too distressed about it... New Dawn, as many rose hybridizers said, is a good hybrid that produces good offspring. The only problem is that there is only one or two seeds per hip. Good news is that they are worthy and generally good. If I were you, just start collecting seeds from whatever rambler and large flower climber you are able to find and start selecting seedlings. If they die early then they weren't worth enough to grow. Disease proneness, lack of fragrance, and very thorny canes are the dominant genes in roses, so don't be discouraged about offspring that are sick and then die. Repeat blooming is a recessive gene, keep that in mind. Its common especially for ramblers. Also try to get the tiny rose "The Fairy" as it has genes from ramblers. It is very small, but lovely. I've noticed that its offspring are variable in nature as some are floribundas, some are ground covers, a tiny few are climbers. It's disease resistant too, and passes on its' genes for it. I think a cross between The Fairy and New Dawn could offer something very intresting. Alas, I won't have New Dawn for a few years. But I have The Fairy and will work with it this season. Just telling you stuff that I've heard and learned from other hybridizers as I don't have any experiance with ramblers.

Use digestive enzymes on the seeds.

In addition to the link given below you may find this link interesting:
http://jrm.library.arizona.edu/data/1951/042/6mccu.pdf

Here is a link that might be useful: Use of digestive enzymes to germinate rose seeds

Rose seeds, particularly from the hardy species, often have a double dormancy. Try planting the seeds in damp sand and keeping them warm (greenhouse temperature) for a month or so, then chilling them (not freezing!) for another month. Then let them warm up.

'Golden Showers' seeds would probably respond to this treatment. Otherwise, if they are only chilled they are inclined to germinate the following autumn.

If you're in a hurry and don't want to mess with after-ripening and chilling, use a tender type -- Teas and Chinas -- pollinated by the hardier once-bloomer (Multiflora hybrids, for example). I once crossed the purple 'Sweet Chariot' x 'Comtesse du Cayla' (yellow/rose blend) and got a seedling with bright red flowers. You could try a yellow Tea (not Hybrid Tea) x 'Veilchenblau' or 'Rosemarie Viaud' and expect something similar, but much larger.

Karl King

Here is a link that might be useful: CybeRose