Does ROAS matter for a Leads campaign?

Short answer: not really, and here’s why
ROAS needs a completed sale to calculate against, but a Leads campaign's job ends the moment someone submits their contact information. Whether that lead turns into revenue depends on what happens after the ad, a sales call, a quote, a follow-up email, not on anything Meta can see or optimize for. Asking ‘what's the ROAS on this Leads campaign’ is really asking a question about your sales process, not your ad account.
Ask your agency this instead

Want the metrics that actually matter for a Leads campaign? Open the tool and pick one.

Other metrics for a Leads campaign
Sources

Adamigo provided the cleanest full Leads-objective breakdown (CTR, CPC, CPM, CPL, conversion rate), cross-checked against Hawky and theedigital, which agreed closely on CTR, CPC, and CPL. CPM bands are synthesized from Adamigo's stated range with the below-average threshold set a bit lower for a more usable spread.