ROAS as a profitability check
ROAS turns ad performance into a simple multiple: how many dollars come back for each dollar spent. Because it is a ratio, you can compare campaigns of any size on equal footing. The key is to read it against your break-even ROAS, since the same 4x can be highly profitable for one business and a loss for another with different margins.
ROAS, margin and growth
Chasing the highest possible ROAS can cap your growth, because the cheapest conversions are limited. Many advertisers deliberately accept a lower ROAS to reach more customers, as long as it stays above break-even. Use ROAS to guide spending decisions, but pair it with margin and lifetime value to see the full picture.