The short answer
Roosta registers alarms with the operating system rather than scheduling them inside the app. That means an alarm fires whether or not Roosta is running — after a force-quit, after a restart, and while a battery saver has suspended background work.
Why alarm apps miss alarms
An alarm app can schedule an alarm in one of two places: inside its own process, or with the operating system. The difference is invisible in the interface and decides whether you wake up.
An app that keeps the schedule in its own process — commonly a timer in JavaScript, or a background worker — is relying on that process still being alive at the right moment. Both iOS and Android are free to suspend or terminate it, and both do so routinely: when memory is tight, when the app has been idle for days, or when a manufacturer battery saver decides it is not needed.
- The app is swiped away from the recents view, and its timer goes with it.
- The phone restarts overnight after an update, and nothing re-registers the alarm.
- A manufacturer battery optimiser puts the app into deep sleep after a few idle days.
- The system reclaims memory during the night and the process is never restored.
What Roosta does instead
When you save an alarm, the schedule is handed straight to the platform alarm service. From that moment the operating system owns it, and Roosta being open, closed or terminated is irrelevant. On Android the alarm is registered as an exact alarm and the ringing experience runs in a foreground service; on iOS it uses the system alarm presentation.
A consequence worth knowing: because the schedule lives outside the app, an alarm you set stays set even if the app crashes on launch the next morning. The failure modes are genuinely separate.
What still needs your help on Android
Native scheduling removes most failure modes but not manufacturer skins, which are unpredictable and occasionally override platform behaviour. Two settings are worth checking once.
- 1Settings → Apps → Roosta → Battery → Unrestricted.
- 2Settings → Apps → Special app access → Alarms & reminders → allow Roosta.
Our help centre has device-specific instructions for Samsung, Xiaomi, OnePlus and Huawei, all of which layer their own process management on top of Android.