Do you have a written lease agreement? The answer to your question may depend on the content and legal validity of any clauses that might pertain to such a situation. You should have an attorney advise you on this and help you find a solution. An attorney could also give you advice on whether there are any other (in addition to your rights as a tenant/roommate) legal reasons that would prevent him from prohibiting a CPS visit of you shared home. For example, if the CPS visit is the result of a court order, any attempt by him to interfere with it might constitute contempt of court or be otherwise illegal and any applicable contract clause that could be interpreted to allow him to restrict such court-ordered visits may be legally invalid and contrary to public policy.
Ordinarily, in most cases a landlord not living on a rented property would no right to prohibit you from having certain visitors although some reasonable restrictions on the length and time of the visit may be valid. In some cases, such a prohibition might constitute a breach of the tenant's right to "quiet enjoyment" of the property (right to right to possess and use the leased property without disturbance).
However, this case is a bit different since the property owner is also your housemate and you are sharing use of the property. In most circumstances, as both the owner and a resident of the home, he likely would have the legal right to prohibit a specific person or company representative from entering his property. However, as a tenant you may also have that right as well as the right to allow someone access to the property.
Why does he object to CPS representatives visiting your home? I suggest you try to resolve this (with the help of an attorney if necessary) and get his permission for them to visit and if you can't, move somewhere else as soon as you can.