to the best of my knowledge, if expeditions were sent, they achieved nothing/very little. as to why that is, the simple answer is it's very difficult to control the berbers beyond the coastline. when the arabs came, they made a pointed effort to move the center of power beyond the traditional coastal region of africa provence when they established their capital at qaywaran. the capital was (obviously) the end point of a caravan stop and oriented the maghreb towards the sahara. even with this new focus, the arabs found it incredibly difficult to subdue the berbers and there were a number of revolts and a semi-autonomous berber state (the aghlabids) was formed very quickly. it is likely that the romans saw little value in looking southward.ut

the reason for this lack of interest (or a reason for even looking south the the maghreb for that matter) is that the trans-saharan trade routes did not develop into the lucrative network it was to become until the emergence of the almohads and almoravids. indeed, beginning with michael brett's work on the subject, leading scholars of the region surmise that the trans-saharan trade was limited to the salt trade of the garamontes in the eastern sahara. the garamontes traded this product with the villages of western africa. control of this salt trade would have been of very little consequence and would not have been worth the effort of provisioning a roman army for a trek across the largest hot desert in the world.

the rise of the trans-saharan networks coincided with the rise of the abbasid caliphate and the demand for slaves in baghdad as the arab conquests stopped and ended the supply of fresh trade. the modern scholarly consensus is that the gold that these networks became famous for followed shortly after the transport of slaves.