Expand Arm Geometry and click on the Turn Arrows tab.
Select the Turn Arrow for each lane as needed based on the number of lanes.
Select Visible by Default to view the turn arrows.
The Offset from intersect sets the closest point of the turn arrow at this distance from the roundabout.
The Minimum distance before crossing sets the minimum distance that the turn arrow is placed from the crossing on the side closest to the roundabout.
The Minimum distance after crossing sets the minimum distance that the turn arrow is placed from the crossing on the side away from the roundabout.
The Length is the length of the turn arrow symbol.
The Width is the width of the turn arrow symbol.