Explaining his findings, the coroner outlined evidence including a message Rifleman Mitchell left on his Facebook page and WhatsApp messages between him and his girlfriend in the hours before his death, and the discovery of a hosepipe in his car which smelt of fumes.
However, Mr McCrisken said he was not satisfied to the required standard for his findings that Lance Corporal Ross intended to end his own life.
"I consider James Ross' death to be an accident," he said.
The findings conclude a three-week inquest at Ballymena Court House.
Rifleman Mitchell and Lance Corporal Ross were both found dead at Abercorn Barracks in Ballykinler, County Down.
Rifleman Mitchell, 20, from London, was found dead in his room on February 10, 2013.
It came just months after another soldier, Lance Corporal James Ross, 30, from Leeds, was also found hanged in his room, on December 8, 2012.
Both soldiers were serving with the 2nd Battalion The Rifles and had previously been on active service in Afghanistan.
The coroner said he found no evidence of bullying or a culture that dissuaded soldiers suffering with their mental health from coming forward.
However, Mr McCrisken said there is "work to be done" to encourage soldiers to come forward to seek help with mental health issues.
Speaking outside court, Lance Corporal Ross' mother Linda Ketcher said she felt the finding about her son was right.
"We have got what we expected, we always knew he never meant to do this, so the findings for us are right. It doesn't make it any easier but it is right," she said.
She urged the Army to "smarten up" and "get it right".
Lawyer Emma Norton, speaking on behalf of both families, told reporters outside court: "Our sons both served in Afghanistan - James was 30-years-old, Darren was just 20-years-old.
"Both were highly thought of, ambitious, respected and much-loved soldiers, brothers and sons [who] both died on a lonely, isolated barracks in circumstances we still struggle to understand.
"Over the last three weeks, we have been horrified by what we have learned but in addition to our sons' deaths, there were eight other episodes of serious self-harm on this unit - soldiers who had served on active operations overseas and who were not being flagged up as at risk or needing help."
An Army Spokesperson said: "Our thoughts remain with the families and friends of James Ross and Darren Mitchell at this difficult time.
“Whilst neither individual was identified as being at risk, improvements have been made to some of the unit level processes in place.
"In light of the coroner’s findings, we will now examine if further changes are needed."