'Cylchdro' means 'cycle' or 'rotation'. 'Trofan' is 'roundabout'. Trofan is what you see on road signs, never 'cylchdro'.
This may be another North/South or dialect thing because "trofan" is "tropic" according to Cysgair and Y Termiadur Addysg. However, it actually gives "cylchfan" for roundabout (which is what I was taught) rather than "cylchdro" which as you say means "rotation".