Have the children all sit around a large sheet (or large sheet of paper) that you have drawn and numbered a large grid on.
Recap what coordinates are, linking to directions and compass points with related vocabulary, turns and related vocabulary and degrees of turn. Then demonstrate how to send the Roamer to a certain coordinate, talking about the directions and turns made in degrees.
Allow children to have a go using the coordinates that you give them.
To extend, use vocabulary related to compass points. You can also make this into a game where children are split into two teams and given two different colour counters. Use two large sponge dice.
Each team takes turns to programme the Roamer to reach a coordinate that is decided by throwing the two dice (reinforcing turns and angles of turn in degrees). They then mark the coordinate reached.
The winning team is the first to get four crosses in their colour in a row, horizontally, vertically or diagonally (a bit like Connect 4).
A fun way to get computing skills into maths teaching and learning!