What primary sources are available for the study of Roman history and what are the limitations of these sources?

Texts from the time are examples of primary sources. Down to 293 B.C., there is a full account of Roman history, year by year, in Books 9 and 10 of Livy.  Unfortunately, Books 11-20 of Livy's great history, covering the remaining years down to 220 B.C., have been lost; and for this period we have to rely on much briefer accounts.  Two Greek historians shed some light on particular episodes: some long excerpts have survived from Books 19 and 20 of the Roman Antiquities by Dionysius of Halicarnassus, which describe the war against Pyrrhus; and in Book 1 of Polybius there is a summary of the First Punic War.

Otherwise, we have to rely on the Periochae (summaries) of the lost books of Livy, and on the short accounts of the period in two later writers: Books 8-12 of Dio Cassius, as summarised by Zonaras, and Book 4 of Orosius.  

Although by this time Greek historians such as Timaeus were taking an interest in the Romans and writing about their conquest of Italy, the Romans themselves had not started to write much either in poetry or in prose, and only a few scraps of Latin literature have survived from this period.

http://www.attalus.org/info/overview.html#:~:text=The%20major%20source%20for%20this%20period%20is%20Cicero%2C,successful%20wars%2C%20the%20Gallic%20Warand%20the%20Civil%20War.

The limitations are mainly time, books often get lost in time which causes us to lose important sources.

were they embroiderers?

the deaths of over a million communist soldiers

post-traumatic stress disorder in veterans