As a result of the Roc board's unanimous recommendation of Fosun's takeover offer, Horizon said it had given notice to Roc terminating the MID.
Shareholders had been due to vote on the $800 million merger at a scheme meeting scheduled for tomorrow.
In a statement Horizon said it had applied for and received orders from the Federal Court of Australia cancelling the scheme meeting of Horizon Oil shareholders and vacating court proceedings scheduled for August 14.
Horizon Oil managing director and CEO Brent Emmett said the board noted and respected Roc's decision to be acquired for cash as a low-risk means of achieving immediate value for its assets, bringing an end to Roc's 15-year history as an Australian Securities Exchange-listed oil and gas company.
"The board believes shareholders in Horizon Oil can look forward to a bright future through value realisation and cashflow generation from Horizon Oil's diversified portfolio of production, development and exploration assets.
"In particular, prospects for our PNG business, which was the focus of Roc's merger ambitions, remain very strong, with encouraging recent progress."