It is not uncommon for roses planted in my garden not to bloom at all their first year. And not to bloom if they've had any setbacks within the last year. Similarly, flowers might be unusually small in these cases.
Roses that are white in color or a simple pink will frequently bloom the same color time after time, but if the rose is a complex color that depends on two pigments, or if it descends from roses such as mutabilis whose pigments change through the development of the flower, I find that all sorts of things can happen to the colors. Temperature, soil moisture, and feeding can all affect color.
