Add some notes about Zircon roller to Fuchsia SDK update docs

Bug: 707030
Change-Id: I77a50eccbfa58c5236330ba9a593fb96192c2c40
Reviewed-on: https://chromium-review.googlesource.com/745821Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Scott Graham <scottmg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512724}

docs/fuchsia_sdk_updates.md

@@ -16,3 +16,10 @@ it's simply a copy of the steps run on the bot above, and so may be out of date.
 In order to sync a Fuchsia tree to the state matching an SDK hash, you can use:
 
 `jiri update https://storage.googleapis.com/fuchsia/jiri/snapshots/SDK_HASH_HERE`
+
+If you are waiting for a Zircon CL to roll into the SDK, you can check the
+status of the [Zircon
+roller](https://luci-scheduler.appspot.com/jobs/fuchsia/zircon-roller).
+Checking the bot's [list of
+CLs](https://fuchsia-review.googlesource.com/q/owner:zircon-roller%40fuchsia-infra.iam.gserviceaccount.com)
+might be useful too.