How do you work with the Product team to get them to commit to a roadmap? How do you "sell" them the idea that it is important?
Convincing your PM partners to accept and fund your product or feature ideas is certainly never easy. The best approach will vary from one company to the next. That said, I've found that a combination of qual and quant works best -- plus some good old-fashioned persuasion techniques and relationship building.
Qual:
What are our customers telling us in our advisory boards, panels or focus groups? Are they reflecting a need/pain point that your product idea solves for? Are they directly asking for or affirming their interest in buying/trialing a product idea you have? Do these customers represent a valuable segment we want to protect or expand into? (Pro tip: Whenever possible, get your PM's in front of customers directly so they're hearing their feedback firsthand; it's more persuasive that way.)
What is the competition doing in this space? How would your product idea or recommendation position us more competitively vs our peers?
What are your Product team's priorities, principles, or strategic pillars? Can you show how your idea directly maps to the things your PM team already cares about the most?
Do you have any partners in Strategy, Finance or Business Operations who can do a rough market sizing or TAM analysis of your top product ideas? This can add analytical heft to your recommendations.
Quant:
Have you conducted market research or customer surveys that reflect high demand for your product or feature idea, or a profound customer need/pain point that your idea addresses?
Does your company already conduct regular customer "pulse" surveys (NPS, C-SAT, etc.)? If so, you might already have a lot of readymade customer verbatims that reflect a need or demand for your product/feature idea.
Do you ever survey your sales org? What are the top feature requests from reps? How do they feel about your idea's potential to unlock incremental budgets?
Relationship angle:
Building personal trust and kinship with your PM partners makes them more likely to embrace PMM's ideas. Never underestimate spending face-to-face time with your PM counterparts for coffee, lunch, happy hour, etc!
Experience angle:
Do you have unique industry or functional wisdom from a prior job/role that you can draw from when fashioning your argument? Draw from your anecdotal outside experiences to position yourself as a trusted domain expert to "fill in the gaps" in PM's knowledge of the market or customer.
Like any department its always risky to commit to something that may fail / not happen. I find it helpful to shift the dialogue from roadmap and talk more about customer problems that are being solved and / or market opportunities that are being addressed. It moves the goal post from we must deliver X next week, month, quarter to how to plan to solve X problem. Further, most companies have some non-agile ie deadline occasion. like a customer event or internal sales kick-off where not sharing about where one is heading is simply a missed opportunity