I think combat roles can be boiled down into just four:
- Interception
- Hunting
- Flanking
- Siege
Interception is filled by ships that trade in maneuverability, armor, endurance and overall firepower for extreme forward linear acceleration and dangerous but generally short lived firepower from forward fixed weapons. They are for nearly immediate defensive response as well as hit and run strikes against enemies relatively close to a base or vessel capable of refueling and rearming them. As such they are usually found standing guard near wormholes, hidden inside asteroid fields, sitting on planetary launchpads or docked en masse with stations and large ships.
Hunting is filled by ships that favor stealth, detection, endurance, moderate armor and considerable but not long lasting firepower. While interceptors quickly deal with close in threats, hunters take their time tracking down long term threats over great distances and are deployed in smaller numbers. They are usually found deployed inside enemy territory near the cover of asteroid fields, debris fields, stars or uninhabited planets as well a good distance from friendly forces serving as a first line of defense.
Flanking ships combine maneuverability, armor and long lasting but close ranged firepower often mounted in turrets or swiveling casemates. They are used to protect friendly forces in tight formations and attack opponents at the closest possible range, where their maneuverability, survivability and flexible firepower allow them to get around or behind the enemy's defenses. Flankers are usually seen deployed en masse in close defensive positions around assets or in small groups near enemy territory forming a second line of defense and standing ready to support friendly hunters caught by patrols in enemy territory.
Siege craft trade in all forms of agility for long ranged, long lasting, fearsome forward firepower as well as detection and possessing good frontal armor but weak flanks and rear. They are used to demolish entire fleets, hardened targets and swathes of infrastructure from a safe distance. Siege craft are usually found near friendly bases for mutual protection or at the center of a flight group.
I have also boiled down the logistical roles into four:
- Aerospace Shuttling
- Space Transportation
- Asteroid Mining
- Gas Mining
Aerospace Shuttling is the movement of cargo between the surface of a planet and orbital altitude. It is especially critical for fringe systems where young colonies require high end necessities they can't yet produce for themselves at full capacity and which don't have space elevators, stations or even enough of their own shuttles to transport goods themselves.
Space Transportation is the movement of cargo between the orbital altitudes of different planets, often located in different solar systems. It is especially critical for mining operations and planets with extreme environments, since these places usually have enormous quantities of a few types of goods and never enough of most everything else they need.
Asteroid Mining is the break down and collection of asteroids for the metal ores they contain. It is dangerous due to the ambient collision threats and the cover against detection they provide to hostile craft.
Gas Mining is the collection of elements from gas giants for use as reaction mass, fuel, coolant and artificial atmospheres. It is dangerous due to super storm turbulence and the inability to quickly escape the gravity well in case of attack.
Note that while many ships fill only one role or two, there is nothing stopping other ships from taking on a number of them.