How do you recommend Product Marketing get looped into conversations earlier to help influence the roadmap, instead of being notified after it's already in development or released and ready for Go-to-Market?

We need to distinguish between what goes into the roadmap [1] and how it is communicated outwards [2].
For [1] establish PMM as a core stakeholder in the product planning process, giving them a regular seat in roadmap discussions. This allows PMM to bring valuable customer insights (VoC, Win/Loss), support data (feature requests, support tickets, and competitive data—and everything around inbound product marketing—before key decisions are made, ensuring features align with market and customer needs.
When it comes to communicating it outbound [2], there are decisions to be made on time horizons, problem grouping, and solution or outcome grouping that PMM as product communication experts, are well versed in and can lead on. From there, shared success metrics can reinforce collaboration and set up integrated planning workflows where PMM reviews potential feature impact, aligning roadmap priorities with GTM success. Finally, establish a feedback loop post-launch to ensure continuous improvement based on real-world results.