Screen.vue

<template lang="html">
	<v-container v-if="clock" class="screen" fluid fill-height>
		{{room.timer}}
	</v-container>
	<v-container v-else class="alert" fluid fill-height>
		Some non-reactive stuff.
	</v-container>
</template>

<script>
import { mapState } from 'vuex';

export default {
	data: () => ({
		clock: true,
	}),
	computed: {
		...mapState({
			room(state) {
				return state.rooms[this.$route.params.roomId * 2 - 1];
			},
		}),
	},
	updated() {
		if (this.room.open && this.clock) {
			this.clock = false;
			// do some non reactive computations
		else {
			this.clock = true;
			// do some computation with the updated state
		}
	},
};
</script>

Ca, ça marche par contre ?!

<template lang="html">
	<v-container v-if="room.open" class="screen" fluid fill-height>
		{{room.timer}}
	</v-container>
	<v-container v-else class="alert" fluid fill-height>
		Some non-reactive stuff.
	</v-container>
</template>

<script>
import { mapState } from 'vuex';
export default {
	computed: {
		...mapState({
			room(state) {
				return state.rooms[this.$route.params.roomId * 2 - 1];
			},
		}),
	},
	updated() {
		if (this.room.open) {
			// do some non reactive computations
		} else {
			// do some computation with the updated state
		}
	},
};
</script>