Roman Leljak (Đurmanec, August 21, 1964) is a Slovenian publicist and researcher of Udbina's archives from Slovenia and the author of a series of books exposing the activities of the former Yugoslav state security service.  He is a leading Slovenian investigator of Yugoslav communist crimes after the end of the Second World War, with extremely significant humane research work on numerous excavations where thousands of innocent people died. He also revealed, for example, the dark secret of the Great Pit.
Roman Leljak was born in Đurmanec near Krapina. He finished elementary school in Šentjur. After primary school in 1978, he continued his education in Sarajevo and Belgrade at the military high school. He completed a specialization in coding in the Yugoslav People's Army (JNA), and then special training on military security in Pancevo.
He published the book "Spidlji Udbe" ("Associates of Udba") and published a list, photos and addresses of all Slovenian Udbas and their associates: - They are in leading positions in banks, large companies, politics, justice and the media. The book states that a total of about 65,000 people worked for the infamous Udba in Slovenia: for example, teachers, journalists and cultural workers. .
According to Leljak's research, about 35% of Slovenes in 2015 were in some way related to Udba. He emphasizes that this part of the Slovenian population regularly gives their vote to the left parties and supports communism. The author emphasizes everything that they got and that today there are 35% of Slovenes they got because someone worked for Udba. Leljak also said that he found a description in the Archives of various methods by which Udba recruited priests.
In 2015, he told members of the Slovenian parliament that the Slovenian Udba had bought lethal weapons in the form of a pen with which it could secretly kill people a few years before Slovenia's independence. One copy was shown publicly in the Assembly. This was followed by a criminal report by far-left leftist Milan Brglez. 
Leljak believes that informants had a privileged status during the communist era, they had the best houses, and children and relatives got good jobs without any problems. The author pointed out that his research showed that 60% of informants were convinced Yugoslav patriots, so they did it out of conviction, while 30% of informants worked for money, and the other 10% were blackmailed and had to cooperate with Udb. According to the author, today all these people are said to have signed, but to have done nothing.  The Association of Croatian Homeland War Veterans 91 (UHBDR91), in cooperation with other Homeland War Associations, led by Mladen Pavković, awarded him the “Great Golden Plaque” (June 7, 2016).