Does ROAS matter for a Traffic campaign?

Short answer: not really, and here’s why
ROAS measures revenue generated per dollar spent, but a Traffic campaign isn't set up to optimize for revenue, it's optimized to get people to click and land on your site as cheaply as possible. Looking at ROAS on a Traffic campaign can be misleading, since Meta isn't trying to find buyers here, it's trying to find clickers. The numbers that actually tell you if this campaign is working are CTR, CPC, and what people do once they land on your site.
Ask your agency this instead

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

Other metrics for a Traffic campaign
Sources

These sources break out Traffic-specific CTR, CPC, and CPM figures that agreed closely with each other. The Conversion Rate bands for this objective are a softer estimate, since Traffic-specific conversion data isn't something the industry publishes much of.