romans in the sahara

The first Roman expedition was made by Lucius Cornelius Balbus, following Augustus wish to expand his Empire.

In 19 BC 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 Niger (Below Hill)
river.

Gaius Suetonius Paulinus made another expedition to what is now southern Maroc (former Spanish Sahara) and Mauretania in 41 AD.

He reached the northern area of the Senegal river and probably the western Niger river's affluents

In the year 41 AD Suetonius Paullinus, afterwards Consul, was the first of the Romans who led an army across Mount Atlas. At the end of a ten days' march he reached the summit,—which even in summer was covered with snow,—and from thence, after passing a desert of black sand and burnt rocks, he arrived at a river called Gerj...he then penetrated into the country of the Canarii and Perorsi, the former of whom inhabited a woody region abounding in elephants and serpents, and the latter were Ethiopians, not far distant from the Pharusii and the river Daras (modern river Senegal)

There are evidences (coins, fibulas) of Roman commerce and contacts in Akjoujt and Tamkartkart near Tichit in actual Mauritania

The third was done a few years before by Julius Maternus, a Roman explorer who reached the lake Chad area and described the abundance of animals like hippopotamus and rhinocerosin that northern Nigerian region. His travel lasted four months.

“Julius Maternus, setting out from Leptis Magna and Garama with the King of the Garamantes, who was beginning an expedition against the Ethiopians, by bearing continuously southward came within four months to Agisymba, the country of the Ethiopians where the rhino is to be found.” 

In the eastern Sahara the Nero expedition to Ethiopia was made: it was an exploratory expedition promoted by the Roman emperor Nero to discover the sources of the Nile River.^[ The expedition was exploratory, according to most scholars. Indeed Seneca wrote that around 62 AD Nero sent some legionaries to the city of Meroe in Nubia in order to explore all the Nile southward from that capital. This expedition was done because he wanted to get information about Equatorial Africa and the possible richness of the area. Another expedition was recorded by Plinius the Elder in 68 AD, but was probably related to military activities in order to gather information for a possible Roman conquest of what is now Sudan.According to most scholars, there it is the strong possibility that both expeditions were the same. This expedition was the first in history from Europe to the interior of equatorial Africa. It probably lasted several months and bypassed the Sudanese swamps called Sudd during the dry season, reaching the northern portion of present day Uganda.

The western coast of Africa was explored by the Romans after the conquest of northern Maroc (then called Mauretania Tingitana): the Roman vassal king Juba II organized a successful trade from the area of Volubilis. Pliny the Elder, a 1st century Roman author and military officer, drawing upon the accounts of Juba II, king of Mauretania, stated that a Roman expedition from Mauritania visited the islands of the archipelago of the Canaries and Madeira around 10 AD and found great ruins but no population, only dogs (from those animals he called the islands, using the latin word "canarius" or "canis" for dog).

Indeed, according to Pliny the Elder, an expedition of Mauretanians sent by Juba II to the archipelago visited the islands: when King Juba II dispatched a contingent to re-open the dye production facility at Mogador (historical name of Essaouira, Morocco) in the early 1st century AD, Juba's naval force was subsequently sent on an exploration of the Canary Islands, Madeira and probably the Cape Verde islands, using Mogador as their mission base.

We have even recorded historically  that, 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. They even knew of the Hesperides : some researchers, like Duane Roller, have even identified the Hesperides with the Lesser Antilles.

Furthermore, according to Pliny the Elder and his citation by Gaius Julius Solinus, the sea voyage time crossing the Gorgades (Cape Verde islands) to the islands of the Ladies of the West ("Hesperides", actual São Tomé and Príncipe and Fernando Po) was around 40 days: this fact has created academic discussions about the possibility of further Roman travels toward Guinea and even the Gulf of Guinea. Indeed, a Roman coin of the emperor Trajan has been found in Congo 

Aelius Gallus in 25 BC 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, since Cornelius Gallus had established a garrison at Arsinoe (near Assab, in actual Eritrea) on the Ethiopian shore. This was the only Roman outpost in eastern Africa south of Egypt and lasted a few decades.