Why are conversion counts in Facebook different than Rockerbox?
Rockerbox is de-duplicating all conversions across all your marketing channels, while Facebook takes full credit for all conversions where it was a touchpoint.
For a path such as: Criteo Display > Facebook > Paid Search > Organic Search
Facebook platform = 1 conversion RB First Touch = 0 RB Last Touch = 0 RB Multitouch = fractional (ex .3)
Conversions, revenue, and by extension ROAS will look lower in Rockerbox than what Facebook self-reports
To more closely compare in-platform Facebook purchases to Facebook credit in Rockerbox, compare total Facebook touchpoints.
You can do this by pulling an MTA Report of user-level log files, or by filtering for Facebook within the Customers > Paths view of the UI.