Romans in sub-Saharan Africa

Roman expeditions to Lake Chad and western Africa were a group of military and commercial expeditions conducted by the Roman Empire across the Sahara Desert, into the interior of Africa and along its coasts. They were made by the Roman Empire between the first and the fourth century. One of the main reasons of the explorations, according to academics like Jonathan Roth, was to procure gold and spices
Characteristics
The Romans organized expeditions to cross the Sahara desert with five different routes:
through the western Sahara, toward the Niger river and Timbuktu.
through the Tibesti mountains, toward Lake Chad and what is modern day Nigeria
through the Nile river, toward modern day Uganda.
though the western coast of Africa, toward the Canary Islands and the Cape Verde islands.
through the Red Sea, toward the Somalia region and potentially Tanzania.
All these expeditions were supported by legionaries and we're mainly for commercial purposes. Only the expedition conducted during emperor Nero's reign is seen as a preparative for the subsequent conquest of Ethiopia or Nubia. In 62 CE, two legionaries explored the sources of the Nile river.
The primary reason for these explorations was to obtain gold and used the camels to transport it.
The explorations near the African western and eastern coasts were supported by ships and deeply related to the naval commerce (mainly toward the Indian Ocean).
History
The first Roman expedition was done by Lucius Cornelius Balbus, following Augustus' wish to expand his Empire. In 19 BCE, he conquered the Garamantes (who lived in the Fezzan of Libya) and sent an expedition under Septimus Flaccus south across the Tibesti mountains, reaching the River Niger.
Gaius Suetonius Paulinus conducted another expedition in the Western Sahara and Mauretania in 41 CE. He reached the northern area of the Senegal river and potentially the western Niger river's affluents.
In 41 CE, Suetonius Paullinus led the first Roman military force across the Atlas Mountains. At the end of a ten day march, he reached the summit. From there, the force crossed the desert, the Gerj River, and then moved into the country of the Canarii and Perorsi, not far distant from the Pharusii and the river Daras (modern river Senegal). Evidence (coins, fibulas) dated to the First Century indicates Roman commerce and contacts in Akjoujt and Tamkartkart, near Tichit in modern day Mauritania.
The third was conducted by Julius Maternus, a Roman explorer who reached the Lake Chad area during a four-month long expedition.
The eastern Sahara expedition was promoted by the emperor Nero, to discover the sources of the Nile River. Seneca wrote that around 62 CE, Nero sent legionaries to the city of Meroe in Nubia in order to explore all the Nile southward from that capital. Another expedition was recorded by Plinius the Elder in 68 CE. This expedition resulted in the first Europeans to reach the interior of equatorial Africa. It probably lasted several months, bypassed the Sudanese swamps and possibly reached the northern portion of present-day Uganda.
The western coast of Africa was explored after the conquest of northern Morocco (then called Mauretania Tingitana). The Roman vassal king, Juba II, organized successful trade from the area of Volubilis. Pliny the Elder, drawing upon the accounts of Juba II, stated that a Roman expedition from Mauritania visited the Canaries and Madeira around 10 CE and found great ruins and only dogs (from those animals he called the islands, using the latin word "canarius" or "canis" for dog).
According to Pliny the Elder, an expedition of Mauretanians sent by Juba II visited the islands. Juba II dispatched a contingent to re-open the dye production facility at Mogador (historical name of Essaouira, Morocco) in the early 1st Century and subsequently explored the Canary Islands, Madeira, and possibly the Cape Verde islands, using Mogador as their base.
According to Pliny the Elder, the Greek Xenophon of Lampsacus stated that the Gorgades (Cape Verde islands) were situated two days from "Hesperu Ceras" (today called Cap-Vert), the westernmost part of the African continent, showing a knowledge of the area by the Romans. He also wrote that the sea voyage time to the Gorgades (Cape Verde islands) and the islands of the Ladies of the West ("Hesperides", modern day Sao Tome and Principe and Fernando Po) was around 40 days. This has generated academic discussions about the possibility of further Roman travels toward modern day Guinea and even the Gulf of Guinea. A Roman coin of the emperor Trajan has been found in Congo.
Aelius Gallus, in 25 BCE, led an expedition across the Red Sea against the Sabaeans of Arabia Felix (modern Yemen). In order to control Sabaea, the Romans took control of both sides of the entrance to the Red Sea, the Bab-el-Mandeb strait. Cornelius Gallus established a garrison at Arsinoe (near Assab, in modern Eritrea) on the Ethiopian shore. This was the only Roman outpost in eastern Africa, south of Egypt and lasted a few decades.
Maritime commerce
In 1 BCE, Augustus decided that the circumnavigation of Africa should be attempted. Two naval outposts were established on the Atlantic coast of Africa. One was located at Sala, near present Rabat, and the second was at Mogador in southern Maroc (north of Agadir). The island of Mogador prospered for the local exploitation of purple (highly esteemed in imperial Rome) until the during the reign of Septimius Severus. Based upon the discovery of a sunken merchant ship from southern Spain in the Djibuti area, Augustus also wanted to organize an expedition from Egypt to Mogador and Sala.
The eastern coast of Africa, south of Egypt, was at the center of a huge sea commerce between Rome and India through the Somali coast. Works, such as the Periplus of the Erythraean Sea and Ptolomey's Geography, list a string of market places along this coast. Finds of Roman-era coins along the coast confirm the existence of this trade that extended to the area of modern day even Tanzania. Geography references the town of Rhapta as metropolis of a political entity called Azania. Archaeologists have not yet succeeded in identifying the location of Rhapta, though many believe it lies deeply buried in the silt of the delta of the Rufiji River.
Felix Chami has found archaeological evidence for extensive Roman trade on Mafija island near the Kenyan coast and on the African mainland, near the mouth of the Rufiji River and the northern Mozambique coast, which he dated to the first few centuries CE.
Roman coins have been found in the area of modern day Zimbabwe and Madagascar, suggesting that Roman vessels sailed south of Azania toward the area of the gold mines of the Zambesi river and the legendary Greater Zimbabwe kingdom.