Bamboo are not like other plants in that they don't benefit from having rootbound roots sliced up; in fact it can set them back. If you've got some loose roots that you can position, I guess that wouldn't hurt, but be careful not to bend them too much. You have two basic options available: 1) unpot the plant and put it in the ground without messing around with the root ball; 2) if you've got that many roots and more than one culm, you might be able to divide it in two with a root saw and have two plants. In general, don't worry about a rootbound bamboo. It will be happy to get out of the pot and will do well all by itself.

Thanks very much for the quick answers. I will just plant and let nature take its course.

R,