House Oakheart of the Riverlands motto is the same as their master house in the form of "Out roots go deep" of which means that they will always dig in and fight to the end wherever they may be which is something was proven when they lost a large part of their force attempting to hold the gate of Tree Hill while everyone else fled.
House Oakheart was founded by Lucas Oakheart after he fell in love with Padme Goodbrooke and married her forming a new house. Alongside Padme the two would work tirelessly to rebuild the area following the disasterous civil war between House Goodbrooke and its vassals. The main elements of the rebels remained a part of their power structure and for this reason Lucas and Padme were forced to remain constantly gaurded as they worked to improve the relationships. Despite a dramatically rebuilt land, and improved diplomacy the rebels begin to plot again, and Lucas was forced to deal with rebels in the country side attacking merchants and travellers trying to destabilize his rule.