The Denver Post reported Thursday that Speaker Crisanta Duran dismissed the complaint by political organizer Thomas Cavaness on Dec. 29 after an investigation by an outside human resources consultant.
In his November complaint, Cavaness claimed that Rosenthal improperly touched him at a fundraiser in 2012, when Rosenthal was campaigning for a House seat.
Rosenthal has called the allegations "baseless and false." He was elected in November 2012.
Duran has declined comment on the case and on another complaint involving Democratic Rep. Steve Lebsock of Thornton, citing confidentiality rules in the Legislature's policy concerning sexual harassment complaints.
"To address even the perception that politics play a role in this process, I have directed any formal complaints to an independent outside party for review and investigation," Duran said in a statement Thursday. "I will continue to follow their guidance on what does — and does not — fall under our policies."
Duran, Republican Senate President Kevin Grantham and other top lawmakers are conducting a review of that policy that is aimed at accountability, increasing openness and protecting those who come forward at a time when lawmakers across the country have been forced to resign over sexual misconduct claims.
The lawmakers voted to hire the Legislature's first human resources employee and increase workplace harassment training. They are also considering creating an independent body to investigate complaints.
Cavaness' attorney, Alan Kennedy-Shaffer, said Cavaness was told of the decision in a conference call in which Duran stated the complaint fell outside the scope of the Legislature's policy. Duran noted the dismissal wasn't an indication of innocence or guilt, and that there may be other options for Cavaness to pursue, Kennedy-Shaffer said.
Duran had suspended Rosenthal from his post as vice chair of the House Local Government Committee pending the investigation, which was conducted by a human resources consultant from the Employers Council. The council offers services in employment law, human resources and other areas.
It wasn't immediately clear if Rosenthal would be reinstated to the post.
Rosenthal's attorney, Harvey Steinberg, on Thursday reiterated past statements that harassment never occurred and that the Legislature had no jurisdiction in the matter since Rosenthal wasn't a member of the House in 2012.
Cavaness said the issue goes beyond a single incident.
"When you are an elected official, it's not just what you do when you are an elected official; it's what happened before and while" someone is a lawmaker, Cavaness told the Post. "You are a leader and have power and authority and should be held above reproach."
The complaint against Lebsock, who is running for state treasurer, was filed by Democratic Rep. Faith Winter of Adams County concerning an incident in May 2016. Lebsock denies the allegation.
Duran removed Lebsock from his post as chair of the Local Government Committee and called on him to resign after Winter filed her complaint.
Duran said Thursday she had recused herself in November from the Lebsock investigation and delegated it to House Majority Leader KC Becker.
This story has been corrected to reflect the correct spelling of attorney Alan Kennedy-Shaffer.