41c is improved thus making caulking processing easier thus the above mentioned inner retaining projections 41g and outer retaining projections 41h can be formed with high precision and the amount of their protrusion can be stabilized thus allowing them to reliably retain rollers 42 fig1 shows said roller and cage assembly being used by fitting onto shaft 45 and outer ring 46 when used in this manner roller 42 makes contact with roller guiding surfaces formed on both sides of the above mentioned thick walled portion 41d roller 42 is then guided nearly over p c d and dimensions are set so that it does not make contact with inner and outer retaining projections 41g and 41h moreover dimensions are also set so that the traveling surface of outer ring 46 and the outer surface of cage 41 make contact before contact is made between the inner surface of cage 41 and shaft 45 in the above mentioned roller and cage assembly cage 41 is made of for example cemented steel scm415 stkm13 and so forth on the other hand ceramics is employed for the material of each of rollers 42 equipped on said roller and cage assembly and said ceramics is for example silicon nitride si 3 n 4 since the roller and cage assembly as claimed in the present invention is equipped with rollers made of ceramics it was confirmed by the following experiment that the temperature rise accompanying its rotation is suppressed to a low level this experiment consisted of placing the.