How can a marketer or marketing team sustainably create content and with ROI in mind?

Business is about sustainability whilst sustainability is about meeting customer needs as a prelude to generate ROI. This calls for adequate customer knowledge; taste and preferences  through persistent  and research that directs d value added and customer driven contents development to match cost of content development and sales forecast or revenue hence a practical formula for generating ROI.

Strategy and infrastructure. Without these, you'll lose steam after a while and never see results. So, resist the urge to sprint out of the gate and create content haphazardly. Pause enough to plan and be strategic, set your goals, learn what will actually attract the right buyer, and then start producing content. I promise you'll run faster and longer if you plan first.

In your planning, you first need a buyer persona. If you don't know your ideal customer and what they are struggling with that you can help solve with your content (as well as your product and service), you don't have product-market fit and will wind up creating content that falls flat.

Once you have your persona built, open a free app like Evernote or Trello that syncs between mobile and desktop. This is your idea pipeline. Whenever ANYTHING hits you (a blog post idea, a stat you hear, a photo you take, anything at all that could be content), you want to save it immediately. This helps you avoid starting your next project from scratch.

Finally, when you're ready to create, start by producing a killer content offer -- this not only ties to your funnel by requiring a business action of the reader, but it allows you to brainstorm tons more content all based from that one single work.