Operating from an Aladdin's cave within St Paul's Church, the resources are not limited to religious material. Teachers have only to decide on a topic and the centre will do the rest.
"We do the whole of equal opportunities - race, gender and disability, " explains Ms Roberts, a centre director and project manager. "We have dolls with crutches or hearing aids, special jigsaws of disabled figures and different races. We're saving up for a dolls' house with a ramp.
"A teacher might say 'This year we're doing Africa'. Now Africa is a huge continent, but we'll do our research and supply music on tape, clothes, materials for display, books, photo-packs, videos, recipes, spices, drums, figurines and artefacts. We also have a tape of animal noises - the teacher reads a story to its accompaniment."
Sixty organisations - and not only schools and colleges - subscribe to the centre. But many more borrow resources on an ad hoc basis.
"We just hire what we need - we get a big box for #163;30," says Paul Gilligan, headteacher of St Joseph's RC primary school in Little Hulton, Salford. He is full of praise for this "resource on our doorstep". And his staff have visited the centre collectively "so they know what's available".
They borrowed a model of a dragon for Chinese New Year and, as a follow-up, the children put on a display of oriental music and dance for parents and pupils. The climax came with a visit to Manchester's vibrant Chinatown, to celebrate the New Year.
"It brings something alive to the children. It makes for an experience, a living thing that remains with them for a long time," says Mr Gilligan. Months later, one six-year-old still presents him with little Chinese biscuits. (Her parents receive them from their Chinese boss.) Other children bring him books or pictures - a clear demonstration that the experience has been effective.
The Little Hulton estate, where most of St Joseph's 181 pupils live, has its share of problems, particularly vandalism. Many of its mostly white inhabitants have come to the estate from inner-city areas and Mr Gilligan likes to think the school is "a little oasis in an area that doesn't have lots of amenities".
He says: "It is up to us to make the children aware of the different communities on their doorstep. We have a responsibility to bring that to life, otherwise they grow up with misconceptions."
Just a few miles away, near Bolton town centre, Barbara Kenny heads a state nursery school with an ethnic make-up that could not be more different. Seventy per cent of the 120 three and four-year-olds at the Alexandra nursery school, Daubhill, are from ethnic minority backgrounds. More than seven languages are spoken - Gujerati, Urdu, Bengali, Punjabi, English, Chinese, Turkish, Arabic and "the odd unusual Indian language".
The Alexandra receives a selection from the resource centre each half-term for its displays on changing topics and festivals.
"We always make sure books, artefacts and resources show a variety of ethnic groups," says Mrs Kenny. "We aim for racial harmony and cultural tolerance by ensuring the children are aware of the diversity of the cultures represented in the school."
With "journeys" as last summer's theme, the school looked at a trip to Africa. Books, clothes and musical instruments were selected. A woman in Zambian national costume visited the school and the children played music on authentic African instruments.
A recent Office for Standards in Education report on the school remarked: "All children are regarded as special and their differing backgrounds and cultural beliefs are respected and celebrated." The report praised the school's use of the resource centre as well as "the extremely positive, purposeful and effective leadership of its headteacher".
Mrs Kenny says: "We make the children aware that each culture is as valuable as the other. "
Ms Roberts, who has run the Resource Centre for nine years - five with funding from local authority and central government and, when that was withdrawn, as an independent project - is delighted at OFSTED's indirect approval.
"Education starts from the cradle and is far more important than legislation," she says.
With two part-time workers and four volunteers, the centre also arranges one-day awareness courses which have been attended by members of the fire, police and probation services. A Holocaust Day - when a Holocaust survivor spoke of his experiences - was attended by teachers from 20 schools.
Ms Roberts and her staff research and write the teaching packs and many of the books themselves, using desk-top publishing. Despite the pressures of constant fund-raising, she finds the independence liberating.
"The world is our oyster. We are open to everyone. Apart from the north-west, we supply to London, Ipswich, Dundee and the Isle of Wight. We have also received orders from Holland and Belgium."
She clearly thrives on what she calls the wealth of culture and the effect it is having. "This year," she points out excitedly, "British Home Stores in Bolton had Chinese New Year handkerchiefs on sale and a local shop sold greetings cards for Diwali (Hindu), Eid (Muslim) and for Chinese New Year."
The Multicultural Resource Centre, St. Pauls, Deansgate, Bolton BL1 4TH. Telfax: 01204 366868. Personal visits are welcome. Open: Tuesday and Friday 10am-4pm; Wednesday and Thursday 11am-6pm.
Annual subscriptions vary, from #163;100 to #163;400, according to the size of the organisation.
Loans are individually priced but vary from #163;1 for a book or tape, to #163;10 for a box of artefacts or a large instrument.
Students with NUS cards receive a 50 per cent discount on many items. Workshops start at #163;50.