Nepenthes can have extensive root systems, N. bicalcarata and N. rajah are two that stick out like sore thumbs when it comes to root mass and plant size. N. mirabilis can be pretty impressive as well. Other, like N. merrilliana have root systems that are more of a "tap root" form and penetrate deeply rather than a fibrous network such as N. bicalcarata and N. rajah.