Yes, Pullips can be rooted. Just too bad Taeyangs and Dals can't be rooted (unless you have a drill, but it may be risky). Pullips used to be rooted until 2004, when they came with wigs. Personally, they look better rooted. Let me tell you how to do it.
YARGH! Look how sloppy the wig here is. And it looks like it barely fits her too. So I had to remove the wig and take the scalp piece out.
Here she is without her scalp. When removing the scalp, make sure to use a butter knife or another type of dull knife, so you won't end up cutting yourself or damaging the scalp in the process..
When the scalp is removed, make sure you paint it the same color as the hair you plan on rooting it with. You can easily poke holes with the thick, sharp end of a rooting tool (highly recommended). Don't use the needle and thread method, nor the knot method, since they don't work well on Pullip scalps. Besides, the rooting tool and glue make things much easier and faster for you. With the shapr end of the rooting tool, poke a hole big enough to fit a strand of hair though and with the thin, hooked end of the rooting tool, push the hair thorugh the hole all the way. When rooting Pullip hair, I recommend nylon, saran or mohair doll hair. Acetate is not recommended because it is to thin and breaks easily.
Here's the scalp completely rooted, but WHAT A MESS! First off however, glue the scalp back on the doll and let it dry. It sometimes helps to put a rubber band over the dolls head to make sure it stays on there. After the glue dries, Brush the hair, then part the hair by bringing a strand of hair on the middle of the scalp (where the part is) and poke it through the hole, creating a part in the scalp. Go right one way and left the other to thatch a part, but make sure the holes at the part are close together. After the part is thatched, use boiling water to wet down the hair, following cold water. Then use a towel to dry the hair and then brush it again. You can do boil perms, cut it or even style it. However, when styling the hair by cutting, cut off a little bit at a time, so it doesn't look all uneven. I strongly recommend you boil and style the hair after you are done thatching the part.
Here's the finished product. Looks much more natural, doesn't it?