Roam is a notetaking tool for networked thought. Roam's API isn't publically available yet, but Intend already has alpha access and is working on an integration. We'll be one of the first apps integrated when the Roam API goes live in the next few months.
In the meantime, you can read this short and beautiful description of how the philosophies of the two apps are harmonious, written by a user of both apps. He took the four headings from the Intend philosophy page, which talks about each of them in more detail and distinguishes Intend's approach from more classic philosophies like Getting Things Done.
Roam is a perfect place to keep your lists and all todo-items. Usually they are out of sight, but pop up here and there. If needed one can with the use of some tagging make elaborate queries in order to find the best tasks to tackle next. It's simply a great planning tool... And here Intend shines now—after the plan has been made, the tasks have been picked, one needs to not forget the big goals. Because reality alters those plans, changes the importance of tasks quickly, and inside Roam one might quickly loose the overview. Not in Intend, which narrows the view on whats most important for oneself.
Where Roam is the encyclopedia, Intend is the syllabus.
Working and living in Roam is very alive, maybe even too much so. Everything ends up in multiple places, every block might become a rabbit-hole. Small tasks show up everywhere, and are never forgotten. Intend helps here because its more stable. Sometimes old tasks "show up", but usually its more a clean slate every day. Like the Daily Page in Roam, but never that full and potentially chaotic.
Where Roam is the soil full of seedlings and seeds, Intend is the orchard.
In Roam, blocks come first. Blocks can be tasks, but unlike random little tasks in a GTD inbox, they're much more likely to be located in-context. But at the end of the day the magic of a blank page waits—which is liberating, but also tends to loose track of all the maybe important internal threads sometimes. While sometimes the "outcomes" page in Intend annoys me at first, its simple enough to be quickly finished and reminds one of those ideas and goals which should be in the mind most of the days.
Where Roam is the wave, Intend is the surfer.
Both Roam and Intend are proactive. But its hard inside Roam to not end up with endless mentions, citations, and thoughts. Thats inspiring and thought-provoking, but sometimes more like Twitter-Feed of ones mind (and those of others). Intend tends to enforce more the search for the adjacent next—maybe not always that inspiring, but usually at least helpful for actually achieving something.
Where Roam is the strategy, Intend is the tactic.