You should put them in the refrigerator for 2 months before you try to get seedlings to grow. That should start at least 4 months before you want to plant them, after they grow 3-4 inches tall. I use a lot and grow them indoors and plant at 6-8 inches. Put in half sun, and Half shade area. My seeds produced half of the 20.

Are these seed already went through startification process? or i have to do it?

Since these seeds require 2 months in your fridge first. I won't start them until October. that is when they will go in the fridge. Then in December I will watch them grow until spring.

How do you suppose to plant these seeds, due to it comes with no instructions?

You're supposed to cold stratify the seeds for 6-10 weeks before planting.

How big do the rose bushes get.

I am not what size the roses will be but, they are already growing fast. I have 4 bushes going in pots and 1 in the ground. I'm in AZ so we are at 115 or above so this heat will set them back. They still look great and healthy.