Everything is, of course, blurry at the edges.
If your job is doing something that basically all companies of that size do, you might be staff. If your job is something that contributes to a product or service that your company sells, you might be line.
If you work on the deployment, monitoring and debugging of the CI that builds your SaaS, are you staff or line?
If you work on the deployment, monitoring and debugging of your CI system that QA uses, are you staff or line?
If you work on the deployment, monitoring and debugging of the point of sale systems that your brick-and-mortar stores need, are you staff or line?
If you work on the security of your company which includes the SaaS that you sell, and sometimes you talk to prospective customers about those security issues, are you staff or line?
The biggest question around all these is: does your company management think much about the staff/line distinction, and how will that affect what they do?