Question
Hi Lynnette

it is a while I've bought 2 small roses (20-25 cm high) but their entire leaves falls from time to time and have no flower.
Do they get much sunlight? or this is a consequence of watering shortage? Should sunlight be direct or indirect for them?
The soil is kind of grain soil (small grains of soil 3mm dimensions).
I don't know what I should describe more for you to find out the problem. I live in Hiroshima, Japan where it's humid now.

Regards,
K1

Answer
I am assuming that you are growing these roses inside the house? If you are then it is the heat and dryness of the house that is causing the roses to drop it's leaves. Mini roses are no different than big garden roses and require the same growing conditions. If you put the little rose in a larger pot ( about 24 cms wide) it will make the roots happier.If you are concerned about the soil, I would buy a package of potting soil and put that in. Sometimes plant nurseries use large lumps of Perilite to help keep the water in the soil but these can be a problem once it is out of the greenhouse.  Soak the pot in water weekly and then let it dry out as roses like a large drink not a lot of small ones. Then mist it daily with water and use a slow release type of fertilizer such as Osmocote 14-14-14 and finally place it in 8 hours of sun and then shade, it will grow well for you. Then every spring cut it right back to about 3 inches an let it make a new rose bush.
However if you are growing the rose outside in a garden, it could be spider mites are attacking the leaves. Look under the leaves and if you see tiny webs then that is the reason the leaves are dropping off. Again mini roses don't want a lot of sun and they don't need it so if it could be planted in 8 hours of sun and then get shade you should see a difference.
Spider mites hate water so simply spraying the whole plant until it drips usually will get rid of them.