The ERP selection process should involve several people from your company at each of the key phases. An ERP project manager should oversee the entire process and be involved at every stage. In addition:
The introduction phase should involve your IT Director.
For the overview demo, you should also include key ERP users, like those from finance or logistics.
During the discovery phase, you'll want to involve your CFO and the COO.
The workshop phase should involve all of your key stakeholders.
For the proposal review stage, as well as the references evaluation and follow-up, most organizations involve their CFO and CEO.
Finally, for the decision, most companies rely on their management team.