About half of the 250 most-watched Roku channels, including CBS All Access, already deliver ads, but in selling that inventory publishers have had to extrapolate audience demographics for ad impressions.
Now, Roku channel partners will be able to measure audience according to Nielsen’s standard demo breakdowns. Nielsen will collect usage data from Roku devices (stripped of personally identifying info) and then will use its National People Meter television panel to assign audiences.
via Nielsen to Measure Roku Connected-TV Video Ads | Variety.