something like (i haven't tested this or written lua in ages so please fix as appropriate)
--[[ -- Asteroid ring one:
Contains asteroid 0-4 ]]--
AddAsteroidRing(5, -4200, 1200, 100, 25000)
-- Asteroid ring two: asteroid 5-6
AddAsteroidRing(2, 4200, -1200, 100, 2500)
-- Asteroid ring three: asteroid 7-8
AddAsteroidRing(2, 8200, -1200, 100, 2500)
for i=1,8,1 do -- where 8 is the number of asteroid you created, and asteroid 0 is the player's
faction = math.random(10) -- get a random fatcion - 10 is just an example, use however many factions you put in the setup
if faction == 1 then faction = 0 end --don't include the player
a = GetAsteroid(i)
a.Owner = faction
a:AddTrees(1,1)
a:AddSeedlings(300)
end
-- Asteroid 0: This one given to the player and has 50 seedlings
a = GetAsteroid(0)
a.Owner = 1
a:AddTrees(1,1)
a:AddSuperSeedlings(300)
a.Moveable = true