Would having a tolerance to roxy effect a tolerance to vicodin?

i want to know how much vicodin i should take, every says 15mg is good. but i have taken roxy a few times and 15mg isn't enough anymore i would prob need 25-20mg of roxy if i had to guess, but i stopped taking it when 15mg didn't work (jus a week or so ago, not real long). will this effect how much vicodin i should take at all (for my first time)? i'm being serious here, if you're going to say don't do any cause it's bad then just hit the red x in the corner