It's a loaded & sorta private question, however I'll give a shot at answering. Yes, you can make money from Ads on Roku. IMHO the criteria, is lower than you're suggesting. I don't think you need to meet numerous standards with some agencies. I believe for Roku's RAF (internal ad server dept) it's something only like you don't get paid until the Quarter AFTER you make $100, or something like that. Which one could expect to make within a reasonable amount of time (weeks or months, depending on viewership numbers).
However, 'How much can one expect to make?' is a different question. This is where it gets a bit private & sensitive to us all, I don't think we ever discuss #'s here. I'll say that in my experience, it's low. Penny's on the dollar imho. When you factor in the time spent coding, creating the logo's & images, uploading content, and money spent on video hosting, I don't believe it'll pay off for you. Even putting that aside it still isn't alot of money, so view it as a hobby or side income.
Also, something you said is a bit unclear, you say you built a mobile app, yet are looking to use DP? Is the app a video only product? People do build & run ads on games for Roku, but you can't build games with DP.