Does ROAS matter for a Engagement campaign?

Short answer: not really, and here’s why
ROAS measures revenue against ad spend, but an Engagement campaign isn't trying to generate a sale, it's trying to generate likes, comments, shares, and views. There's no revenue event to measure this against. If revenue is the actual goal, this budget belongs in a Sales campaign instead.
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Other metrics for a Engagement campaign
Sources

Adamigo provided the Engagement-objective CTR, CPC, and CPM figures used here, along with explicit engagement-rate tier language that informed how the bands were set.