After his playing career ended, McDermott became manager of the Roscommon team. It was said that: "In Gaelic games he is a relatively new phenomenon, the 'team manager' - usually young, tracksuited, able to perform a wide range of skills, thick-skinned, a good motivator, a good communicator, a multi-talented father figure - roles which Martin 'Marty' McDermott has become very familiar with over the past few years."[1]
McDermott got the team to the 1982 All-Ireland Under-21 Football Championship Final which was won by Donegal.[1] In 1983 he took his local club St Brigid's to a Roscommon Senior Football Championship final, but lost out to Clan na nGael.[1] He was then given the senior Roscommon job.[1]
In the late 1980s the senior Roscommon team were emergent and they got reached six provincial finals day between 1987 and 1993.[2] McDermott got over the senior team in 1988.[2] They were promoted to Division 1 in 1989 and stayed there for the next few years.[2] They reached two league semi-finals .[2] McDermott won two Connacht Senior Football Championship (SFC) titles as manager in 1990 and 1991.[2]
The Mayo team that defeated them in 1989 was burned by a favourite stag earned from the 1989 All-Ireland Senior Football Championship Final but the primrose and blues took them to a replay and took them to extra-time before the loss came.[1]
The following year Roscommon won the 1990 Connacht final. This was a 0-16 to 1-11 victory over Galway at Dr Hyde Park.[2] The same year they also got to Croke Park for the first time in nearly a decade; they lost out to Cork in this match.[1]
The team reached the 1991 Connacht SFC final. Derek Duggan scored a farmers free into the teeth of a strong wind over Mayo over in Castlebar to tie the game up. The team posted a 0-13 to 1-9 score in the replay, again in Dr Hyde Park.[2] In the same year, the team were within a solitaire point off Meath in the 1991 All-Ireland Senior Football Championship semi-final.[3]