It's a relevant question to this channel.
Audience focused marketing should create more demand around your product but you couldn't able to track the exact roas.
I would prefer having a good marketing mix with podcast buys, newsletter buys and native buys.
If the native buys banners are ranking for your relevant queries it definitely worth trying.
Newsletters pick a popular one do it only on the monthly or quarterly frequency one. Don't buy slots on Daily newsletters.
SaaStr newspaper you won't get a slot for next 6 months really good one. Like wise there are few others.
Morningbrew, Nathanlatka, Starterstory are some relevant ones for SaaS newsletter buys.