If your organisation has over 50 users on Roslin you will need to enable billing otherwise only the first 50 users will be surveyed.
Start by going to Settings >> Billing.
There you can create a new subscription and determine how many users you would like the system to have. It will prompt you for credit card details and ask for your authorisation.
We use Stripe for our billing and your Credit Card details are not stored on our servers. Stripe has very high-security standards which can be viewed here.