Advice needed: How and when am I supposed to do an ROI report for a start up that did not start selling yet? I will not promote

I’m developing my first business currently and it’s a B2B. I have no prior finance knowledge or business experience so forgive me if my question is ignorant or has an obvious answer. I’m wondering at what stage am I supposed to do an ROI estimate? I have a cost report available, but the product has not been launched yet. If I can do it now, how is an ROI report done when the product is not properly priced yet? And is it even possible?