While the Romans had lots of written laws (see for example The Twelve Tables), they did not have a constitution that told them how to run the state. Instead, they strongly relied on tradition, the mos maiorum, as it was called. Nevertheless, things did change, most importantly one has to discern between three phases:
Of Etruscan times there are very few, if any, accounts and we mainly know legends and myths; the offices described here were created and most important during the Republic. Under the imperial bureaucracy they
lost most of their importance and independence.
The Romans had some rather modern ideas:
- Annuity - officials were elected on a yearly basis.
- Collegiality - there was always more than one person of the same rank to prevent abuse.
- One person could not hold the same office twice and not more than one at the same time.
- During his term, an officeholder enjoyed immunity - however, afterwards he could be held responsible for his actions.
The elections took place at various gatherings; only free men had the right to vote.
A list of the Roman offices roughly in order of decreasing power:
(the short description is in no way exhaustive, hopefully there'll be a full writeup on each some wonderful day)
- Censores - the most esteemed office, only for
ex-consules. Their most important duty was holding the census.
- Consules - commanders of the
military and general replacements for a king. There were always 2
consules, except in cases of emergency, when a dictator could be
appointed for a time of 6 months.
- Praetores - administrators of the legal process
- Quaestores - tax collectors and administrators of the
treasury
- Aediles curules - police, also caring for the patrician
temples and patrician games
Those were only for the Roman nobility, the patricii.
The working class plebeii had 2 offices of their own:
- Tribuni plebis - a very powerful office, they could
theoretically veto everything. Their job was to protect the interests
of the plebs.
- Aediles plebis - police, also caring for the plebeian
temples and plebeian games
The usual career, the Romans called it cursus honorum, of a
successful politician was first quaestor, then maybe some military
office, then aedile or tribune, then praetor and finally
consul. After his term was over, an officeholder could leave the city of Rome and
work on in a province as a proconsul, propraetor or proquaestor
with the same powers. Many could also become members of the Roman Senate later on.
Finally, there were many assistants, called apparitores. They
were not elected, but wage-earning jobs. Most important were the
- Lictores - bodyguards for the higher officials carrying
the fasces, the symbols of power. The higher the office, to more lictores an officeholder was entitled to have.
and the
- Haruspices - told the will of the gods from the
entrails of sacrificed animals (auspicium), a very important job in
fact!
Others were
- Scribae - scribes
- Viatores - messengers
- Praecones - heralds
- Pullarii - guardians over the holy chickens (I kid you not!)
- servi publici - slaves of the state, for carrying stuff, doing
odd jobs and firefighting (a real problem in ancient Rome, see Nero ;)
The Romans had for the time a very advanced political system. However it was not as neat and tidy as it seems on paper. It worked rather well in the early Republic, when Rome was more of a city state. But in the late Republic it suffered from widespread corruption and with enough public or military support one could always bend the rules as one saw fit, see for example Sulla, Pompey or Caesar. This led to a series of civil wars and finally the replacement of the Republic by the Empire.
Resources: http://www.imperiumromanum.com/index.htm | 
