By the standards of his later evangelical beliefs, he considered his Methodist upbringing to be both liberal and without a clear presentation of the Christian gospel.

"[3]: 19  Sider observes that the foundations of later values began to take shape at this point: a commitment to combine evangelical ministry with social action,[3]: 19  together with recognition and service to all true people of God, irrespective of church affiliation.

Sparks' teaching on organic church life and the work of the cross in the believer made a great impression on Forster.

[3]: 22  [2] Ichthus began with "elements of Brethren ecclesiology, an acceptance of second blessing theology, a willingness to engage in spiritual warfare, [and] a recognition that the church was big and varied rather than narrow and sectarian.

[13] According to Andrew Walker, a leading commentator on the British New Church Movement he was considered to have "one of the finest minds in the Evangelical constituency.

"[14] Theologian and author Greg Boyd dedicated his 2007 book The Jesus Legend to Forster, stating that "for fifty years Roger has tirelessly and selflessly served the Kingdom with intellectual brilliance and Christ-like sacrifice.

[21] with Dr Paul Marston with Graham Kendrick, Gerald Coates and Lynn Green with Faith Forster articles, chapters and forewords popular academic