I think even in a fully healthy lineup, you could probably fit Robertson into one of the twelve available roster spots up front. Assuming Clifford's gone and every other forward is back and healthy, you could do:
Hyman - Matthews - Marner
Mikheyev - Tavares - Nylander
Johnsson - Kerfoot - Kapanen
Robertson - Engvall - Spezza
...and then who's Robertson bumping out that should be in the lineup ahead of him? Malgin? Gauthier? Petan?
And if this year has been any indication, we'll count ourselves very lucky if we ever have a fully healthy lineup. With Johnsson out for the rest of the year, it's not going to happen a single time this entire season. So there will be times when extra opportunity would be there for him.