In order to make your enemies as your allies just follow this. First, build a 
very vast military base. Don't concentrate on creating extra villagers. If you
are playing a random map with more than two enemies then one of them will be 
concentrating to build a forward military base like you and the other will be
concentrating in creating extra villagers to build temples, markets and Wonder.
This you could easily see from the mini-map. Now bring your large army to the 
enemy base who concentrates on creating villagers, destroy their wonder and 
temples. The enemy at once gets stunned to see your ambush attack and they will
change their diplomatic stance to ally. Atonce you should set your diplomacy 
to ally if you are too late then they will again set their stance to enemy. Try
it,It really happens. This technique is common to both Age of Empires-I and 
Age of Empires-Rise of Rome. If more doubts persists, Mail me.