Campaign Length, Power Level, and Themes
I'd like to shoot for at least 5 sessions for this particular game and perhaps as many as 10, provided that we enjoy ourselves and schedules work out. That makes the whole campaign around three months at the outside. Given how easy it is to have superheroes drop in or out of a specific session,though, don't worry overmuch if you can't commit to every single week.
We'll need to discuss what day we play as a group, but my current inclination is toward Saturday afternoons.
Let's use the default Power Level of 10 for this game. While I considered starting at PL 8, its simpler for new players to use archetypes and quickstart characters if we use PL 10. In benchmark terms, that puts your PCs around the level of Green Arrow, Black Canary, or the Teen Titans. You can look at your heroes being experienced human adventurers OR talented but neophyte metahumans.
Conceptually, your heroes should be either native to St. Roch or out-of-towners who've decided to make it their new home. You can be practically any stripe of hero, just so long as they can function in a gritty variety of superhero story, have a motive to help St. Roch's citizens, and are willing to work with other heroes. I like Crime Fighters a lot, personally, but a Gadgeteer, Mystic, or even a Paragon can work, provided you give them the right "St. Roch" spin.
While the real tenor and focus of the game depends on your choices as individuals and as a group, I'd like to emphasize the following themes:
St. Roch parallels New Orleans' long association with Catholicism, voodoo, and mysticism. Swamp Thing - "the Life Entity's Champion" - lives in Houma, which is just across the Mississippi, and you can bet that there are vampires, demons, ghosts, and werewolves running around the city as well.
As such, a good percentage of the weirdness you encounter will have spiritual or magical elements. Perhaps your hero is supernatural themselves, is devoted to a particular faith, or has had face-to-face encounters with beings of myth and folklore.
St. Roch's population is mostly composed of decent, hardworking men and women, but its had a long association with dirty politics and moral degredation. Some of this is clearly linked to its financial decline in the 20th century, but some of it seems endemic to the culture and atmosphere of the city. Bribery scandals, mismanaged bureaucracies, and vices of all kinds seem to flourish there.
The challenges your heroes will face might come from both sides of the legal fence; crooked cops and greedy businessmen can be just as bad as some yahoo in a costume holding up the local bank. Your hero may also have a few stains on his or her character, flaws which can create inner or external conflict.
Where there's desperation there's crime, and there are a lot of desperate people in St. Roch. Many of these crooks are minor league street hustlers, junkies, and dope slingers, but others have amassed enough power and prestige to run entire neighborhoods. When they have disagreements, people die, often simply because they were in the wrong place at the wrong time. Every day, the body count rises.
Can your heroes stem the tide of violence on St. Roch's streets? What are their methods? Do they address the root causes of this problem? Consider also how crime may have impacted your hero in their past.
A bit more abstract than the other themes, "rebirth" can refer to personal redemption, spiritual growth, or helping St. Roch out of the quagmire its been in for decades. As dark and strange as things are likely to get in this city, there's a lot of people, history and culture worth saving and nurturing. Whether through economic redevelopment, stamping out corruption, or honest-to-God miracles, there will be opportunities to renew St. Roch's promise.
Your hero may be personally involved in business plans to revive the local economy and job growth, or they could just try and bring some hope to inhabitants on the block where they grew up, but either way you should have an investment in the future of St. Roch. Also consider the possibility of reviving the legacy of forgotten heroes, being literally reborn (superheroes do that all the damn time), or simply some sort of transformation you may personally attain.
Let me know if you have further questions!