Two Separate Business Accounts

We have two separate Grasshopper business accounts. One is medical related and one is a roofing company. Is there a way to have both numbers ring to the same phones? These are for the owner of the businesses and office manager of the businesses. I don't see a way to have two Grasshopper apps on the phones. Call are being received, but is it. that you have to switch between the two daily? The owner is logged into the medical business account and receives calls. The office manager is logged into the roofing company and receives those. Each is set up to roll over to the other person's phone if they don't answer. The rollover is not happening to the other person. 

TIA