Hi-
Not that I am an expert in anyway, but this might get you started...
The rostata may set seed (if you have hummingbirds). With heliconias, the seed will be in the colorful part of the flower- it will probably stick out a bit. It is ready to pick when it is blueberry blue. Wipe the blue part away, plant the whitish seed inside right away. It will take months to sprout. I have not tried rostrata seeds yet, but have a number of seedlings from other varieties, so it is possible. Heliconia seeds are most viable the fresher they are.
I have had a lot of luck with ginger seeds too. The gingers will set seed- where the seeds are located depends on the variety. Torch ginger seed pods are easy to see, (big pods right on the flower head), other types you have to look around inside the dead flower for them. Of the 4 varieties I have tried, all have sprouted in 1 month. I assume fresher is better, but I tried 1 type after the flower head was dried and they still sprouted.
Hope this helps, Gwenn

As a beginner I got the same idea of producing seeds to exchange with others from all kind of gingers & heliconias I have now in my garden
but you can look for previous Q&A on the forum - specially some answers like the following one from Tim Chapman
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> Lack of natural pollinators is probably the problem (of not producing seeds). Some Heliconia have very specific species of hummingbirds as pollinators. They have adapted to each other, and you won't have these in (your area). You could try hand pollination. I would imagine, like gingers this is best done in the morning. I've never pollinated Heliconia, though I've done many different gingers.
> > ****************

Really? I didn't know ginger give out seeds, I just bought the root at Vons and dipped it in hormone (rooting stuff) and I'm looking for reasults.