I've had my fair share of growing roses at home and I think the key is to provide them with the right conditions. For soil, I use a mix that's specifically designed for roses, it's usually a bit more acidic and has good drainage. As for the pot size, I'd say go for something that's at least 12-15 inches deep to give the roots enough room to grow. Roses generally love sunlight, so if you can, place them outdoors where they can get at least 6 hours of direct sunlight a day. I've tried growing them indoors, but they just don't do as well, they need that direct sunlight to thrive.