The short answer to your question is that many Roman slaves did in fact run away, and this was generally considered a problem by slaveholders. Some slaves may have chosen not to run because of the difficulty in succeeding and because of the harsh punishments caught runaways received, while many others were willing to risk these things.

Recovering runaways was considered the slaveholder's responsibility. Egyptian papyri are a good source for this. In one (P. Oxy. 1643), the slaveholder appoints someone to find his runaway in Alexandria, and present him to the authorities for punishment when found. These papyri also give evidence for slaveholders posting notices and offering rewards for the return of runaways, with detailed physical descriptions (1). These practices are also seen in laws, as recorded by Ulpian (Digest 11.4.18a). Though it was the slaveholder's responsibility to recover runaways, they could count on support from local soldiers, officials, or the provincial governor. There were also professional slavecatchers.

Travel itself was slow and dangerous in ancient Rome. A runaway would likely not have much money and would have limited provisions. It would be hard to find safe sleeping accommodations and food while on the run, and travel would not be fast without proper access to pack animals and carts (or even the main road). We do have a folk legend of runaways dedicating stolen food to the tomb of Drimakos, a famous runaway, so theft was an option used (2). In general, it would be difficult to get far away. Slaves were denied the legal and familial network of protections that a free person used in building a life, which could make starting over difficult. It was also a serious legal offense to aid a runaway, and there were even fines for government officials who received a petition and didn't help in the search (3). Even distance or the passage of time were not guarantees of freedom as long as the owner lived and could use his network to search (4).

This is to say that it was not uncommon for runaways to be caught because of the difficulty of a fugitive life and the mechanisms in place for recovering runaways. In Seneca's Letters 4.4, he recounts how some runaways commit suicide instead of being recaptured. Other evidence that runaways were caught is in Digest 21.1, which lists runaway attempts as something a seller must disclose. Slaves who ran away could be harshly punished with crucification or other torturous deaths, or sentenced to work in the notorious mines or mills. In addition, they could also be branded or tattooed in order to mark them as slaves and deter other escape attempts. While this could be done routinely to any slaves, it was prevalent for runaways, especially tattoos on the face (5). Metal slave collars like this famous one might have replaced face tattoos after Constantine outlawed the practice (6).

Roman literature and law are full of examples of slaves running away and of owners trying to recover them. Slaves frequently tried to run away. What might have stopped some is the difficulty of a fugitive life and the harsh treatment they would receive if recaptured. Plenty found escaping their bondage worth the risk, though.

Sources:

(1) Keith Bradley (1994) Slavery and Society at Rome, 118-120

(2) See Chapter 1 of Sara Forsdyke (2012) Slaves Tell Tales: And Other Episodes in the Politics of Popular Culture in Ancient Greece

(3) Alan Watson (1987) Roman Slave Law, 131-2

(4) Keith Bradley (1989) Slavery and rebellion in the Roman world, 140 B.C.-70 B.C., 35

(5) Deborah Kamen, "A Corpus of Inscriptions Representing Slave Marks in Antiquity." Memoirs of the American Academy in Rome, vol. 55, 2010, pp. 95–110.

(6) Jennifer Glancy (2002) Slavery in Early Christianity