Roadmaps are an inevitability. Most of the time someone from administration will want you to have one on file. What happens to them after they get put on file is anyone's guess. But, I find that it's nice to go through the exercise anyway, if you're a big picture type person. I have a very low-tech method. I print out however many months worth of calendars, tape them together into a single sheet of ever-flowing dates, make note of major holidays or activities that will disrupt my flow (really only important if you have seniors and you need to keep track of all their odds and ends that pop up at the end of the year) and note grading period milestones. I'll map out the upcoming week in detail, jot some vague ideas for the week after that and continue. For dates way in the future I'll jot down a note of where I would like to be in the material. If I don't hit it, not a huge deal, put it helps set a pace. If you have a district that is more involved as to when you must teach what, this may not work for you.
Proves it worth in later school years when you're trying to remember just how far you did or didn't get before, especially if you haven't taught a particular prep in a while.
Here's the roadmap I made for Pre-Cal this past spring. It starts with February because I didn't come up with the idea until then. Clicking it will bring up a mega-huge version.