Traditionally the roadmap is filled with set of releases and each release has features and functions. Internally and externally, everyone got used to this format and while there is nothing wrong with this, good product managers make this content better with more context. Let me explain what I mean by this.
Good product managers always study the industry trends, opportunities and present it along with the roadmap. Sometimes they may not even call it a roadmap but this is part of their business strategy. When they plan for the next product iterations, they consider below topics. This is not to say that Product Managers dont think about this, but bringing it explicitly on the roadmap makes it more interesting for its consumers.
What industry does this product serve? or is this product a horizontal play - that can be used by many industries. Don't solve the problem for the wrong industry. Many times, its just the matter of identifying the industry and appropriately managing the messaging. Force fitting into an industry is the dangerous part.
What's the problem
What problem does this product solve? One pitfall with the problem statement is NOT to be generic enough. Every company when it starts, resources are limited and this means we need to focus on a specific problem to get customers and build the cash flow.
Once we understand the full or partial problem, the solution must be divided into smaller chunks that are easy to deliver and get validated from the market (customers, users and partners). The biggest challenge is should this theme be fully developed or do we need all themes semi-baked. As an example, If you are making first release of smartphone (and you don't know how market would respond), would you spend all your resources on making the best of phone, camera, GPS Maps, flash, radio, media player, storage,...? or would you just focus on phone and camera? with an incremental plan. Sometimes, companies get into this illusion that they *can* create all the themes and they spend so much time in created half-baked product, in the end the product serves no one.
Buyers vs. Users
People who gives you the check may not be the end user. There are several nuances based on the B2B and B2C scenario but very important to understand who are the buyers, influencers and users. e.g. A company's IT Director buys a Business Intelligence software and a IT analyst is the user. I paid for my smartphone and I am the user. Your sales play, marketing lingo and product design has a big impact on what you know.
There are many other topics that I can mention, but above four are important to consider as a part of the roadmap. Instead of thinking about just features and functions, think about after i release this product "The in the will be able to better manager or solve his . This will help him save <x%>of time and that could translate to <$Y>." It is the time to think more than features and functions. Your product, sales, marketing and customers needs a better language to understand your company's and product's vision.</x%>
Note : Thinking about problem, solution, industry and users is more relevant to the new product development. While PMs from a matured product do think about all these factors, the intensity and important will vary. With the new products, the challenge is the industry validation and with the mature products the challenge is the revenue expansion.