Hi Earl,
You should not (usually) hear "Radar Contact" from a tower unless they are simulating a radar certified tower (which is usually only at large fields afaik). Provided departure control is available (APP/DEP/CTR) you should hear it prior to being given any instructions, since as a radar controller you should not issue any instructions to an aircraft you have not positively identified. You will also usually hear it when entering controlled airspace (from an airstrip, etc) when first contacting a radar controller (APP/CTR) after flying through an area of no control (due either to lack of staff or area procedures).
Again, the first "radar" controller should tell you you are "radar contact", and state your position (and indicated altitude if you have not yet reported it), but a Tower usually should not on VATSIM (with the above stated exceptions).