Because of my brain injury, my ability to imagine things is difficult. Because of that, I decided to flesh out the Roman Afterworlds. What people think are the Roman Afterworlds were copied wholesale from the Greeks. What I came up with is based partially on Roman traditions, which leaves out any details of an afterworld.
The traditional entrance to the Underworld is the Mundus (the Pit). During the three days that the Mundus is opened, the Dead could roam freely among the living. Therefore the entrance and exit to the Roman Underworld would be the Mundus. This is the place the Newly Dead would head to when they died. The living could enter the Underworld through the Mundus.
The Mundus also serves as an underground granary and altar for Consus, the God of the Granary. When the Mundus is opened, He is concerned with the safety of the living. Therefore, Consus guards the entrance with Seia (Goddess of Sown Grain Seeds) and Tutilina (Goddess of Stored Grain). Consus would note the comings and goings of the Dead, ensuring that the grain stores are not disturbed.
Meanwhile, Mania Genita, the Goddess of the Dead, ensures that no Dead leave the Underworld except on appointed days (the Parentalia, Caristia, and Lemuria). Furthermore, She oversees the Lars, Gods of the Household and Families. The Lars are the Dead who watch over their former families. They roam freely among the living to protect their families and others.
Libitina, the Goddess of Corpses and Funerals would conduct the Newly Dead from their dying to the Underworld. At her temple, Romans did keep their registers of their dead. They also stored the equipment for burials to be borrowed by mourners there.
Once the Dead enter the Underworld, they are greeted by the Fates (Parcae). Morta, the Goddess of Death (of the Parcae) decides where the Dead go next. Poena, the Goddess of Punishment will take the impious Dead with Her. The virtuous Dead will be taken by Vediovis, a God of the Underworld and of Plagues.
Poena punishes the impious Dead by depositing them in disease producing swamps. In the middle of these swamps are volcanoes, with vents that emit hot gasses and poisonous vapors. Mefitis, the Goddess of Stench and Sewers, governs this place. She oversees the agony of the impious Dead, who cannot leave. Ill and gaunt, they wander about unable to find any rest.
Meanwhile, Vediovis takes the virtuous Dead to a place of land of amber fields and sparkling springs. Under the sky of an autumn afternoon, it is always harvest time. Thus, the virtuous Dead do not want for anything.
These Dead live in neighborhoods with their clans and families. Their houses are stone with large porches to sit outside. Each home has simple but comfortable furniture. They also contain a large mirror for the Dead to watch their descendants. The houses surround a magnificent garden which has a large mirror in its midst. This particular mirror allows the Dead to go into the world of the living when needed.
This afterlife would be peopled by people who follow the Roman religion. The Heroes of Rome would be there, along with the various Roman kings and consuls. Since they were deified, the Emperors would be with the Gods.
The virtuous Dead would enjoy the sciences and the arts. They would argue philosophy and hold athletic contests. They would be involved with the pursuits of their descendants.
This part of the Underworld is self-governing. The Gods of the Underworld are more concerned with the treasures and the fertility of the earth. Therefore, They have the virtuous Dead set their own laws.
In Roman tradition, the Dead are involved with the living. In my Afterworld imagining, I give the Dead a place to be instead of roaming the world. The virtuous Dead can leave to tend to their families, but the impious Dead cannot leave their miserable volcanic swamp.