Here are the classes, structs, unions and interfaces with brief descriptions:

RFitModes
RFitOptions
RGFitPointType
RAffine2D
RAnimSequence3D
RContour
RContourBase
RContourBase1D
RContourBase2D
RContourBaseCircle
RContourBaseEllipse
RContourBaseGate
RContourBasePolygon
RContourList
RDico
RExtremaFinder
RFitBase1D
RFitBase2D
RFitData1D
RFitData2D
RFitDataBase
RFitDataDecay
RFitDataGaus2D
RFitDataPeak
RFitDecay
RFitGaus2D
RFitPeak
RGBaseRequester
RGColorNumberSelect
RGContourEdit
RGContourListEdit
RGFillAttrSelect
RGFillStyleSelect
RGFitBase1D
RGFitBase2D
RGFitDecay
RGFitDisplayer
RGFitDisplayer1D
RGFitDisplayer2D
RGFitGaus2D
RGFitPeak
RGFrameEvent
RGGetPoints
RGHistoLimits
RGHistoPlotAttrSelect
RGHistoPlotModeSelect
RGHistoTools
RGHistoWindow
RGItem
RGItemListBox
RGItemSelectionBox
RGItemTreeSelector
RGLineAttrSelect
RGListRequester
RGMarkerAttrSelect
RGMessageRequester
RGPadPrintCommand
RGPrintRequester
RGStringRequester
RGTestWidget
RGTextMessageRequester
RGTreeRequester
RGuiFitDecay
RGuiFitGaus2D
RGuiFitPeak
RGZoomPanel1D
RHoughTransform
RHoughTransform3D
RMatrix2D
RObject
RootFitDecay
RootFitGaus2D
RootFitPeak
RPointMark
RRealSampleFFT
RSolidTesselation
RSphereTesselation
RString
RTesselationPoint
RTesselationSegment
RVector2D