Its technically not gestation as the eggs arent fertalized until they are being layed.
But the time between pairing and laying can vary greatly, not only between species, but between individuals of the same. A lot has to do with timing, sometimes externals roles have a lot to do with it as there are many species where mimicing warmer/colder and wetter/drier can play a significant role.
A rose hair (i cant see your pic to know if its rosea, porteri or one of the other chilean species commonly labeled as rose hair) does everything slowly, so i doubt you will be hurrying much up. Ive heard a year to two seems to be a common timeframe....although it could be less of course, but i wouldnt hold my breath.
Other species like P. cam or N. incei for example, may lay 3 to 5 weeks after and be hatched into 1i just 28 days later and 2i and ready to sell 3 weeks after that....but thats not gonna happen with a rosie.