Keep in mind when planting that Rocket red is thought of as very hardy, so this plant will tend to survive through freezing conditions. Rocket red requires a loamy soil with a ph of 6.0 - 7.0 - it grows best in weakly acidic soil to neutral soil.
By our calculations, you should look at sowing Rocket red about 56 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Rocket red is a very hardy plant.