Without adding any bulk, aka compost or other organic matter, then your option is to fertilize. And modern roses are pretty heavy feeders so fertilizing annually (at least) should be part of your maintenance regime.

Various suppliers offer organic rose fertilizers - Espoma, Dr. Earth, Gardner & Bloome, etc.

Back when I grew a lot of roses, I also had rabbits and used bunny poo as my primary rose amendment. Since bunny poo is just barely recycled alfalfa and afalfa is well known as a good rose fert, you could supplement with alfalfa meal or tea. But I also mulched heavily with compost each season so additional outside fertilization was not necessary.

Mulch and manure if you have access. In the fall leaves are wonderful in the garden. I used to save my leaves until spring then mulch on top so they didn’t blow away. The worms happily turn it all to plant food.

Yes, I would have my soil tested, but also apply some alfalfa tea.

Any nutrient source whether tea or petrochemical will impact soil fertility, so that use of such should therefore be based on having had some kind of specific indication of what level that fertility is at established beforehand.

Embothrium

Any nutrient source whether tea or petrochemical will impact soil fertility, so that use of such should therefore be based on having had some kind of specific indication of what level that fertility is at established beforehand

In 7th grade, we learned how to diagram sentences. I believe this ^^^ sentence can be diagrammed successfully. It would serve as a wonderful final exam challenge.

Fish fertilizer or seaweed extract are great mild fertilizers that are liquids, so easy to apply & don‘t add bulk. You could also use a stronger granular fertilizer, just make sure you don’t buy one of the “2 in 1” or “3 in 1” types that also have fungicide and/or insecticide in them. Good luck!

I'm newer to roses but I grow a ton...a ton...of other plants and my favorite all time soil amendment is John and Bob's 'Blend' and I also use their 'Penetrate' occasionally. I don't use any other fertilizers or anything except my own compost that I make from kitchen and yard scraps etc. Blend basically adds microbial life to the soil and helps any kind of plants grow.

Thanks to all of you. These are great suggestions. I do think I will start with a soil sample, get the results, and act. The fertilizers mentioned are great ideas too.

@sybidybl What was the result of your fertilizer project? I have a similar situation with aging roses not doing well.