The teenage pair have spent the past couple of months at the Sir Tom Finney Stadium on work experience.
They have helped Brig maintain their promotion push in the NPL Premier Division.
At the beginning of December, they topped the table and remain in fourth spot - two points behind leaders Matlock Town.
Striker Rodwell-Grant and left-back Coulton have impressed at Irongate. They will be looking to force their way into the plans of PNE boss Ryan Lowe.
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