No, multiple resources in one reservations aren’t possible. Firstly because the plugin is build from ground up on the fact that a reservation is attached to one and only one resource. But secondly, and maybe more important, it would make the configuration a lot more complicated. To define which information get asked per resource and which per reservation and how the resources related information appear in email or invoice would just be the start.
As a compensation there is the function to make multiple reservations and submit them together.