A well-string stabilizing system comprising: a retractable and extendable roller reamer positioned on a string, the retractable and extendable roller reamer configured to support and centralize the string within a wellbore, wherein the roller reamer comprises a plurality of independently controlled rollers; an extension and retraction mechanism configured to extend and retract the roller reamer; a respective hydraulic power unit (310, 312, 314) operatively coupled to each roller and configured to retract or extend at least one of the plurality of rollers and to control the extension and retraction mechanism; a plurality of sensors positioned on or within the roller reamer, the plurality of sensors configured to detect parameters of the well-string stabilizing system; and a controller operatively coupled to the hydraulic power unit and the plurality of sensors, the controller configured to be positioned in the wellbore, the controller configured to receive a plurality of signals from the plurality of sensors, the plurality of signals representing the parameters detected by the plurality of sensors, identify the parameters represented by the plurality of signals, and adjust a well-string stabilizing operation in response to the received plurality of signals, wherein adjusting a parameter of a well-string stabilizing operation comprises adjusting the retractable and extendable roller reamer. a retractable and extendable roller reamer positioned on a string, the retractable and extendable roller reamer configured to support and centralize the string within a wellbore, wherein the roller reamer comprises a plurality of independently controlled rollers; an extension and retraction mechanism configured to extend and retract the roller reamer; a respective hydraulic power unit (310, 312, 314) operatively coupled to each roller and configured to retract or extend at least one of the plurality of rollers and to control the extension and retraction mechanism; a plurality of sensors positioned on or within the roller reamer, the plurality of sensors configured to detect parameters of the well-string stabilizing system; and a controller operatively coupled to the hydraulic power unit and the plurality of sensors, the controller configured to be positioned in the wellbore, the controller configured to receive a plurality of signals from the plurality of sensors, the plurality of signals representing the parameters detected by the plurality of sensors, identify the parameters represented by the plurality of signals, and adjust a well-string stabilizing operation in response to the received plurality of signals, wherein adjusting a parameter of a well-string stabilizing operation comprises adjusting the retractable and extendable roller reamer. receive a plurality of signals from the plurality of sensors, the plurality of signals representing the parameters detected by the plurality of sensors, identify the parameters represented by the plurality of signals, and adjust a well-string stabilizing operation in response to the received plurality of signals, wherein adjusting a parameter of a well-string stabilizing operation comprises adjusting the retractable and extendable roller reamer.