Depends on where you are in that line (which I assume you mean gate for entry to the park), how fast you move and how busy the park is the day you visit. If you're at the front and move quickly, probably about 5-10 minutes. If lots of people are ahead of you and you don't move that quickly, about 20-30 minutes.
Being at rope drop is important, but where you are at rope drop makes a big difference, too.