Opening the RTPI's National Planning Conference this week, Mr Roberts said:
'The government has produced an astonishing series of statements and consultative documents, all set within a framework of overwhelmingly positive political rhetoric - the most encouraging I have encountered in my 30-plus years in the business.
'The institute has welcomed virtually all the government's initiatives. But we have some criticisms. We are less confident than the government about the adequacy of its basically very welcome moves to firm up the regional dimension of planning.
'Are we really serious about regional planning? If so, it is very much down to the sort of people here today to make it work.'
Planning is about changing the world, not accepting it.
'Our time frame is a long one - not just years but a decade or longer, since the lead time to significant development modification is now so long.
'We (politicians and professionals alike) are the custodians of the future. This emphasis must be maintained and we will have to fight for it against strong pressures for quick fixes, cheapskate solutions, rushed decisions.
Planning, said Mr Roberts, must promote physical identity.
'In simple terms people should know where they are. Towns, cities, villages and the countryside should be so clearly identifiable.
'These clear distinctions, completely taken for granted in the UK, are a major product of the post-war planning system - and it is something which must continue.'
Planners were also addressing the issue of sustainability 'in social and economic terms rather than being some doom-laden, puritanical sacrifice.
'It is this attempt to make sustainable development practical, of contemporary political relevance, which separates us from from those who see it primarily as a campaign to somehow save the planet from the depravations of human beings.'
Sustainability was leading to a new orthodoxy for modern planning - the first major shift for 50 years.
'Instead of the segregation of land uses, we increasingly advocate mixed use. Green belts are questioned because of their impact on travel and density - green wedges separating development along public transport corridors is more sustainable.'