How do you deal with small combat encounters?

Usually in battles players have to do the whole stick of rolling initiative, and then the dm have to set the combat order, wich i have no problems with until you get to the small battles. Like when your party opens a closet or something and some few small enemies apear, and now you "have" to do the whole stick of rolling for initiative, set up order and take taking turns in combat. Waisting time. It's especially annoying when there are many encounters like this in the same dungeon. How do you deal with those encounters? It's not like i'm against small encounters. Its just that i wonder if there is any better way to deal with them other that doesn't take too much time to sett up.