Phuong, I'm just bumping this up, as I can't really help. Hopefully someone can. Otherwise try posting on the Antique roses site. It has a lot of traffic.

Winter's are pretty warm here, but not like yours. I prune towards the end of winter. I mostly grow Teas, which do well in warm climates, and pruning isn't really an issue. Do you grow them or Hybrid Teas?

Trish

I wouldn't think winter, I would think resting period. Roses usually bloom in flushes. I would wait until the rose looks like it is resting because it only has mostly dead flowers on it. Then I would pick that time to prune it back by a third.

Thanks for the advicces. Do you think it's ok to prune during rainy season? I have the idea because I notice that it grows crazily in that period, as long as I take care of the notorious black spot

You usually prune a rose when it isn't growing vigorously. Pruning always will activate a rose to make new growth so I wouldn't cut it when it is putting out new growth.

I think most Californians prune in January and February, which is (usually) their rainy season. I would think that would work for you too. If it's really hot most roses go semi dormant anyway. I would think that would be the best time for pruning. As Oldrosarian said, pruning will start new growth so maybe wait until towards the end of your rainy/hot season. They should start putting out good new growth as it cools down and dries off a bit.