How does sugammadex (a modified cyclodextrin) draw rocuronium into its lipophilic cavity?
After consulting with a professor, the answer seems obvious.

The two negative charges repel each other when the free cyclodextrin molecule is in solution, resulting in an "open" conformation that has the carboxylate groups facing "out". The thioether chains interact with the rocuronium as it is drawn into the large open face of the molecule. As the positively charged nitrogen moves into place, the carboxylate groups "close", and lock the drug into place.