Colonial age is FUN in battles. You got the Grandelir, which is an AWESOME troop. Its heavy, but it can hit from a double space! So he dont get damage back on his hit. Always try to use that.
You add with him 7 rogues. Which means you MUST have Alcatraz, to produce tons of rogues.
Specific tactics:
IF the other side don't have artillery, its the easiest battle. You make a small block of rogues(+1 Grandalier) in the left side (where you start) on the upper or lower side. That will force the enemy to come to you, you wait till the other side hit a few of your rogues, and then you hit him back and wipe at least half of the enemy troops on the first attack rotation.
IF the other side have artilery, its harder. Then you have to push through the enemy, hitting the Musketeers first (as they annihilate heavy troops), and hit the artillery ASAP (as they also kill grandiliar fast).
If one of your troops is hit, try to keep it at the back, to save it.