I got it to work by adding an extra level of curly brackets and a comma after the closing square bracket:
{
module: "MMM-ResRobot",
position: "top_left",
header: "Departures",
config: {
routes: [
{
from: "740015972", to: "740061189"
}
],
skipMinutes: 0,
maximumEntries: 6,
truncateAfter: 5,
apiKey: "xxxx"
}
},
Is the example config on https://github.com/Alvinger/MMM-ResRobot incorrect?