Baptism can be done by anyone if done with valid form (Trinitarian), matter (water) and intent (I want this person baptized) in an extraordinary circumstance--the ordinary minister for the sacrament is an ordained minister, whether bishop, priest or deacon. Because Baptism is a sacrament that is ordinarily necessary for our salvation, the Church has allowed others to perform it in dire situations (ie, nurses at hospitals baptizing dying/stillborn infants).
Sacramentals, on the other hand, cannot be truly blessed unless by an ordained minister. There is no "extraordinary" ministers of sacramental blessings, because there is no real urgency in having such things blessed. While it is nice to have a blessed rosary, it is not necessary for the rosary to be blessed in order to have graces poured out on you for using it, or even to attain the "equal" amount of graces as with a blessed object--a non-blessed rosary that you pray whole-heartedly, truly meditating upon the mysteries of our salvation, will bring you more blessings than a quickie half-hearted rosary said on blessed beads that make you too confident on the "power" of the beads themselves just because they are blessed.... sacramental blessings aren't magic, and the item blessed is GOOD to have, but not NECESSARY to have for our salvation.
Thus, while I suppose if we want to we can certainly sprinkle holy water on our objects, houses, whatever, in a wish to express that we would like the blessing of God's grace to come upon it, it is by no means considered an "authentic" blessing by the Church--only an ordained minister, by the power of Holy Orders, can intend to bless something and therefore have it become truly and objectively blessed.
Hope this helps,
"Keep your eyes fixed upon Jesus, who inspires and perfects our faith"
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