In Gabriel wrote:
Did anyone try to raise them in containers with 100%
organic treatment ?

No. Organic fertilisers in pots would be a tricky balance. Ideally the
liquid fertilisers like Miracle Gro would get the best results. You
could certainly try with slower release manures or bone meal, but the
nutrient balance isn't complete from them.

I've recently fed alfalfa pellets to my potted roses, and they are all
shooting like mad from the base of the plants. Quite amazing. I had my
suspicions that alfalfa (lucerne) did this to my ground based plants,
but my pots have proved the theory in no uncertain terms.


If they get sick, is there an increased chance
they will spread the disease to the other plants as well ?

Other roses, yes. Other plants, no.


Since
containers dry very quickly, does that increase disease casualties ?

Indirectly, yes. Weaken any plant and its disease resistance will
suffer too. On the other hand, pots can avoid some fungi and diseases
that spread through open soil.