I think the Trump campaign briefly engaged Stone back in 2015; someone put them wise (or perhaps DJT had a bad feeling) and they severed ties with him. IIRC he was involved with the campaign for a month or two at most.
Trump never hired Roger Stone to run his campaign. They certainly talked a lot, but he did not employ stone.
From the article:
“Stone said Greenberg was alone at the meeting. But Greenberg said he was accompanied by a Ukrainian friend he identified only as Alexei, who he said had been fired from a job with the Clinton Foundation, a global charitable organization founded by Hillary Clinton’s husband, former president Bill Clinton. Greenberg provided no evidence the man had worked for the Clinton Foundation, and a foundation spokesman said the group has never employed a man with the first name of Alexei.
“He was very upset, and he wants to tell his story,” Greenberg said in a text. “He told Mr. Stone what he knew and what he want.”
Greenberg denied that he asked for money, saying that it was his friend who spoke with Stone....
In a separate interview, Stone said: “I didn’t realize it was an FBI sting operation at the time, but it sure looks like one now.”