Currently the in sheet dexterity roll looks like this (replace all '...' with the characters name or 'selected' for a universal macro):
&{template:fantasyage_generic} {{character_name=@{...|character_name}}} {{character_id=@{...|character_id}}} {{name=Dexterity}} {{Result=[[3d6 + @{...|Dexterity} + @{...|Dex_Focus}]]}}
If you simply add the command to add the roll to the tracker:
&{tracker}
After the desired roll it should work (assuming the tracker is open and the player has their token selected)
&{template:fantasyage_generic} {{character_name=@{...|character_name}}} {{character_id=@{...|character_id}}} {{name=Dexterity}} {{Result=[[3d6 + @{...|Dexterity} + @{...|Dex_Focus} &{tracker}]]}}
also, as this isn't an API question i'll move it to specific use.