When you are starting to put numbers together for what your upcoming project will cost, it is very important to know if rock is present and blasting will be needed so it can be accounted for in the budget.
Having an engineering company do soil samples and probes is an option, but is not as reliable as having having a drilling and blasting company come out and probe the site with test holes.
The more information you can gather, the better your budget for rock removal will be!