My company has plans to build and run an enterprise SAAS product and I'd like to get some insight into the typical size and structure of the team required to implement such a project.

I know I'm skipping over a lot of the detail here, but what I can say is that it will be providing a mission critical service to the users, so uptime, reliability and security will be paramount.

The product will feature a REST API, web user interface and some additional command line tools. Users will be a mixture of service accounts (for automation) & actual users doing stuff in the app.

I know my question is fairly vague, but I'd really appreciate feedback regarding what kind of team would be required, such as Project managers, product owners, devs, testers, devops engineers etc.. Along with any references/resources linking to information on this kind of subject.

Thanks!