Excuse for thread necromancy, but I've browsed the scripts and turns out if you refuse to help the little people you get 0 change in alignment.
It's possible for both Romans and Celts to get both rewards, as follows:
1. Leave herbs in the hut east of Ruined Hall (+10),
2. Give the ant ring to sprite north of Spire (+10),
3. Help the little people (+10),
4. Collect the good reward,
5. Rob the wolf hunter (-8),
6. Attack the GIFT sentry (-5),
7. Kill GIFT babies (-15),
8. Don't give Conn money (-5),
9. Rob the bound selkie (-10),
10. Kill the trapped gryphon (-10),
11. Rob the beggar near Nethergate (-10),
12. Collect the evil reward.
The remaining alignment-changing actions are:
1. Take items from the stone circle east of Crone Caverns (-5, don't do this as it reduces your party's dexterity by 1!),
2. Attack the hungry fomorian near Bazaar (-5, Roman-exclusive).