Thanks for your question,
Please clarify if I have misunderstood your question, if you are trying to use the Symphony Elements Checkboxes then you will recieve a response for each end-user that responds back to the checkbox form & submits (via button) their feedback.
The response will be sent back to your Symphony bot application, so you will need to can handle the response from the checkboxes and decide on the next steps - whether it is to create a new room or send a message.
You can find out more on Symphony Elements Checkboxes here: https://docs.developers.symphony.com/building-bots-on-symphony/messages/overview-of-messageml/symphony-elements-1/checkbox
Symphony do not offer a Symphony Elements for Room Picker - it is only possible for Person Selector which can be found here: https://docs.developers.symphony.com/building-bots-on-symphony/messages/overview-of-messageml/symphony-elements-1/person-selector
If you can let me know if this helps - otherwise you are more than welcome to reach out to me directly on the Symphony Develop2 sandbox environment and we can review your scenario.
Feel free to reply if you have any questions or feedback.