My roses have done well in wood chips and bagged leaves. Just start collecting. Are you near the water? What about seaweeds.
Jim

If others are growing roses in the same dirt than you can too. Plant in loosened soil, backfilling with same soil that came out of hole and then putting organic material on top afterward - as mulch. Some may think that because it disappears much faster in tropics there is no point, actually it shows that if anything there is MORE of a need to keep supplying it than in northern climates.

Wow, what a zone change! What fun - congratulations!
Gypsum is supposed to help clay too. I tried it but was never sure how much it worked. Mulch on top heavy and let the worms do the rest.

Wow, rubrifolia, you get around. Last we heard from you, you were in NYC hunting for authors and planning a fir hedge.
How'd you get on down to Puerto Rico?
You have described my soil to a T. Always thought it was caused by the nearby river. Here's what I do.
You are never going to fix the whole place. Plant grass. It does not mind the clay.
When you want a rose hole, dig out a hole 1.5 deep by 1.5 feet wide and long. Here, we only have 8 inches of topsoil, then you hit sandstone and other nasty stuff. So you drag your son off his computer and get him out there with a pickaxe. After all the grumbling, he gets into it. Whack! Whack, whack, whack!
These darn kids these days. Why do they brush their teeth at the breakfast table?
My husband made me a dirt strainer. It is a rectangle built out of 2 by 2's with wire screen tacked on.
Okay we work with a garden cart hooked to a lawn mower and a wheelbarrow. We shovel some dirt on top of the dirt strainer. Rub and work the dirt through the strainer into the lawn cart. It looks like nice dirt when you're done, but it's deceptive. The rocks get dumped into the wheelbarrow.
Then add one half manure to this strained dirt. I have horse manure, which is pretty weak fertilizer.
Then dump it back into the hole and plant your rose.
I had this old recipe that I got out of an old rose book written by a famous rosarian back in the 60's. He called for one third peat moss, one third horse manure, and one third dirt. He claimed roses liked a little clay and to throw some bones if you had them in the hole. He said to make your hole two feet deep. I cheat. I also have my doubts about the peat moss, since straight clay is already acidic. My ph is 7.
This soil plays out quickly so you have to resort to chemical intervention. Did you ever read about how cotton destroyed the clay soils in the South and George Washington Carver convinced them to grow peanuts? So everybody grew peanuts but couldn't sell them so he invented peanut butter? Went to Congress and told them all about peanut butter?
Well, that's everything I can think of about naturally occurring concrete. Until tomorrow.
So................how about a picture of your place in Puerto Rico?

Gypsum flocculates alkaline clays only.

But we had so much more to learn from you about growing roses at the edge of their margins of survival....ah well, now we can hear about the other extreme.
A quick look at the geology of Puerto Rico and I can't help at all.
Perhaps a look at what roses grow as natives on the Deccan basalts of India. Some of the Viru V roses from Roses Unlimited would give you the repeating heat tolerant roses roses. Maybe some searches for the British Empire gardening how to's from the 1800's when there was a feeling that European plants maybe could be grown in the heat of India.
Can you get a good detailed soil test with a consulting lab that will give more than NKP and that might talk about what it takes to get the nutrients out of the soil and into the plants?
So glad to hear that you've landed in an interesting place.

thanks all. yes there is a very active USDA presence here. The island is full of small working farms. Composting is a way of life with the constant rains/runoff.

Since we are close to the top of one of the island's highest mountains, temps here stay in the 70s to 80s & there are always thermals. Not too extreme for rose or for me!

What I am concerned about with the idea of hole/amended soil is the mother of all bathtub effects.

There is a small hole dug by some little boys attempting a pond....and pond it does inasmuch as it will take up to half a day to drain. Ergo I can visualise roses simply floating in their amended soil bath.

Thus I came up with the idea of individualized raised beds.

As of yet broadband doesnt get up here, soooo it will be a bit till we post pix.

Slow drainage is drainage nonetheless. (At least in my clay.)
When we put our orchard in (the original orchard in the 1800's had been across the road but that's now a deer run) I chose a flat-ish area in front of the old barn. We put in pears, apples, cherries (and foolishly apricots and plums). Some of these are in Rosaceae and have some similar growth needs to roses.
Anyway, drainage varied tremendously as we were digging holes and planting.
It was later than a nonagenarian grandson of the owners asked me what ever happened to the ponds that his family had back by the barn. "All filled in" was all I could reply. When we get really heavy rain, there are two flatish areas back there that hold water longer, but it does drain out in less than a day. And the trees in the orchard don't mind, although it worried me a lot.
As long as it drains without becoming stagnant. (And if it were to become stagnant, you'd recognize the 'back canals of Bangkok' anaerobic scent.

When you dig down, do you see clay that's altered by standing water? Or is it fresh smelling all the way down?

Can you start by putting in a close to multiflora rose? In our part of the world, multiflora often lives along streams with its roots in wet zones, but the wet aren't stagnant. And there's a subspecies growth form of multiflora from Mt. Fuji (which is as volcanic as they get and which may have similar clays to yours.) Just a thought.